During dinner, the women of the household suddenly started talking about underwear.
It began when Tiamat curiously asked Shirou why modern underwear came in so many different styles.
Shirou hemmed and hawed, unsure how to answer, until he finally managed, "I guess... it's about how it makes you feel?"
"How it makes you feel?"
Tiamat tilted her head and sank into thought. Then, as if she had suddenly figured it out, she clasped Shirou's hands tightly.
"I think Mother understands!"
"What exactly did you understand?" Shirou asked guiltily.
"Pretty underwear is meant to make Shirou happy when Mother breastfeeds..."
"Cough, cough, cough, cough! Cough, cough, cough, cough, cough!"
Shirou cut off her explosive declaration with a violent coughing fit.
Tiamat immediately began patting the boy's back with a worried expression.
"Y-yes, that's it! Girls feel better just by putting on pretty underwear! How I feel has nothing to do with it. Anything is fine!"
Sakura Matou looked at Shirou, who was desperately trying to cover something up, then glanced at Tiamat before suddenly speaking.
"Tia-san, would you like to come with us to the lingerie store in Shinto tomorrow? All the underwear you're wearing right now was borrowed from Irisviel-san, wasn't it?"
"Can I?"
"Of course. Rider-san and I were already planning to go shopping for underwear tomorrow. It'd be even better if Tia-san came with us."
"Mother wants to go!" Tiamat's starry eyes sparkled.
"Come to think of it, Rider is borrowing Sakura's underwear too."
Since staying completely silent would have seemed strange, Shirou carefully tested the boundaries of the girls' conversation.
At that, Rider shook her head.
"No. Some of Sakura's underwear is the wrong size. Not only can I not wear it, but it barely fits her anymore either."
"Even for a girl as good at putting up with discomfort as Sakura, she's reached her limit."
"......"
So that was it.
Shirou had thought Sakura seemed to be getting fuller by the day, but whenever he looked carefully, her chest didn't seem to have changed that much.
So she'd actually been forcing herself into bras that no longer fit!
My eyes really weren't wrong after all!
"Senpai, you're breathing awfully fast."
Rider immediately answered for him. "It's because he realized Sakura's breasts have gotten bigger."
"Shirou may look careless, but he pays very close attention to things like this."
"Wh-what?!"
Shirou and Sakura cried out at the same time.
Shirou was shocked. Sakura was furious.
"Rider! Don't tell Senpai things like that!"
"There's no point hiding it anymore."
Rider continued with a perfectly serious expression. "Sakura, you should make proper use of your greatest weapon."
"Instead of hiding it, openly displaying it can be a strategy too."
"It'll make things awkward for Senpai!"
"R-right... Yeah, that would definitely be awkward for me."
Actually, it wouldn't be awkward at all. Please tell me more about Sakura's physical measurements, Rider-sama.
Rider gave him a sultry smile. "Oh my... I don't think this is a bad thing at all. If anything, it should be cause for celebration."
"At the very least, someone in this household is bound to be upset about it."
She cast a sidelong glance at the black-haired girl with twin tails sitting directly across from her.
"No way... Tohsaka-senpai wouldn't get angry over something like that."
Sakura Matou guiltily stole a glance at Rin Tohsaka, whose expression had already turned extremely sour.
Without changing expression, Rider poured even more fuel on the fire with words that threatened to start a bloodbath.
"Rin is only human too."
"Of course she'd care about Sakura being blessed with a constitution where her weight stays the same while her breasts keep growing. Especially since the two of them are blood relatives."
"For Rin, Sakura's constitution must be a barrier more unyielding than any fortress wall."
Before the Amamiya family's living room could turn into a Singularity, Shirou decided it was time to retreat.
Rider's voice followed him from behind.
"Therefore, Shirou, you should come help Sakura choose her underwear tomorrow."
"Huh? I'm not going!" Shirou refused immediately.
"S-Senpai is coming too?" Sakura Matou asked, looking embarrassed.
She was mortified at the thought, yet at the same time she wanted Shirou to choose her underwear for her. The two contradictory feelings were waging war inside her head.
"Shirou, you won't come?" Tiamat looked at him with tears welling in her eyes.
"No, no, no! Looking at me like that isn't going to work!"
Tiamat wiped the corner of her eye. "Mother... is a useless mother... sniff."
Shirou's resolve crumbled.
"......I'll go as far as the entrance with you. But I'm not going inside, okay?"
"Shirou! I love you the most!"
Tiamat tackled the boy onto the tatami.
The overwhelming Monstrous Strength transmitted through the slender arms wrapped around him immediately made Shirou regret what he had just said.
Just linger at the entrance without going inside?
Shirou knew perfectly well there was no chance things would actually work out that way.
...
...
The next day.
Inside a lingerie store in a shopping mall in Shinto.
......I've been tricked.
Shirou sat on one of the chairs in the waiting area with a look of utter despair.
That Rider had assured him there would definitely be other men accompanying their female companions in a lingerie store...
Yet there wasn't a single other male creature in the entire place!
There was technically nothing inappropriate about him being there, but a high school boy openly walking into a lingerie store still attracted plenty of attention.
The four of them had now split into pairs.
Sakura and Rider were together, while Shirou was paired with Tia.
Sakura still wasn't mentally prepared to choose underwear in front of Shirou, so she planned to narrow down her choices first and show them to him afterward.
As for Tiamat, an enthusiastic sales clerk had swept her away five minutes ago.
Just as Shirou was wondering whether he should seize the opportunity to escape...
"Shirou! Look at this. Mother thinks this one is very pretty. Would it make you happy?"
"Guh!"
Shirou could feel the piercing stares of the female customers around him. Some of them had even started whispering among themselves.
"Are they really mother and son? They don't look alike at all. The mother is gorgeous, but the son looks completely ordinary."
"I think the boy is pretty cute. He's my type."
"Paid dating? Sugar mommy?"
"Huh? Isn't he still in high school?"
Give me a break. If I'd known this would happen, I would've gone to a mall in the neighboring city instead of Shinto.
Shirou covered his face.
What if I run into someone from school?
I'm here helping my underclasswoman buy lingerie... Would that explanation work?
Of course it wouldn't!
"Tia, that one is a little too much. I'm starting to question the motives of whoever recommended it to you."
Tiamat was holding a matching set of lace lingerie.
The design was incredibly daring, like something that belonged in an erotic magazine.
The fabric barely covered two-thirds of the breasts, and large sections of it were semitransparent.
If Tiamat wore that...
"The sales clerk said this kind of underwear makes boys happiest."
"...So that was your selection criterion."
"Shirou, would you be happy if Mother wore this?"
Tiamat stared at Shirou with complete seriousness.
The female customers around them were staring at Shirou as though he were a sex offender.
If he nodded here, Shirou would probably die socially on the spot.
But compared with what strangers thought, Shirou cared more about his own desires...
No. That wasn't it.
What Shirou cared about more was responding honestly to Tiamat's feelings, without the slightest pretense.
"Yeah. I'd be happy."
"Okay. Then Mother will choose this one."
Tiamat happily carried the lingerie back to the sales clerk, while Shirou found himself looking forward to tonight's "late-night snack."
"Shirou, come over here for a moment."
He had barely seen Tiamat off when Rider's voice called out to him.
Hey! Don't shout my name across a lingerie store!
The female customers started whispering again. For the first time in his life, Shirou felt apologetic about having his own name.
".........Phew."
Shirou pressed a hand to his chest and took a deep breath.
Stay calm. Stay calm.
So what if a bunch of women I don't know point at me and whisper?
If everyone ends up happy, a little misunderstanding like this is nothing.
Besides... Tiamat may have no common sense, but Sakura is different. I know her.
I know exactly what she likes.
Sakura has always preferred plain cotton underwear, simple and understated, just like her reserved personality. Modest, comforting...
"Uh, Sakura... what exactly is that scrap of fabric you're holding?"
Shirou stared at her in disbelief.
It wasn't quite as outrageous as the lingerie Tiamat had chosen, but after agonizing over her options, Sakura Matou had somehow settled on a rather daring design herself.
Mature lace decorated the edges of the cups, giving it the sort of design that could drive a man crazy.
With a bashful expression, Sakura Matou asked Shirou for his opinion.
"Senpai, what do you think of this one? Does it suit me?"
"......"
Shirou had only one question.
Where did my adorable underclasswoman who only wore plain cotton underwear go?
He glared at Rider, who was standing beside Sakura Matou.
It was you, wasn't it?! You're the culprit who corrupted my innocent underclasswoman!
Shirou dragged Rider into a nearby corner.
Rider merely shrugged. "With Sakura's current bust size, it's difficult to find cute styles like the ones Rin wears."
"So that's why you recommended something more mature?" Shirou whispered.
Rider nodded and countered, "Sakura has plenty of potential. There's nothing wrong with taking her style in a sexier direction, is there?"
After a brief hesitation, Shirou still objected.
"No. She's still only a middle schooler."
"Her body certainly can't be called that of a middle schooler anymore..."
"If you want someone to blame, blame yourself, Shirou. You're the one who kept feeding her delicious food until she became this curvy."
"This is my fault?!"
Rider returned to Sakura Matou's side, took the lingerie from her hands, and then...
"Look, Shirou. If Sakura wore it, it would probably look something like this."
She held the matching set of mature lingerie against Sakura Matou's chest.
"!!"
Shirou and Sakura Matou both widened their eyes.
A stir also ran through the surrounding customers.
"Say something, Shirou."
Rider urged him on.
Being used as a makeshift lingerie model only made Sakura Matou even more embarrassed.
"S-Senpai? What do you think?"
When Shirou still didn't give her the approval she wanted, Sakura's voice began to sink.
"Ah... I guess it really doesn't suit me after all. A plain, forgettable girl like me should just stick to plain cotton underwear..."
"I'm sorry. I got carried away... I'm really sorry. I'm just an invisible nobody worth even less than my brother and grandfather..."
"It looks pretty good, Sakura."
Just before Sakura Matou could fully descend into her negative mode, Shirou hit the switch.
A faint light returned to the girl's eyes.
"R-really?! Senpai!"
Shirou nodded firmly. "Yeah. Sakura is already cute to begin with. There's nothing wrong with wearing something a little fancier."
"For a beauty in the making like Sakura, sticking to nothing but plain cotton underwear almost feels like a waste."
I'm so sorry, cotton underwear! I've been insulting you nonstop for a while now.
"B-beauty?! I'm not... Senpai, you're exaggerating way too much. Hehe."
The girl's cheeks turned bright red.
After that, Sakura Matou cheerfully took the lingerie over to the sales clerk as well.
"...Phew."
Having finally seen off another troublesome young lady, Shirou breathed a sigh of relief.
Thank goodness he was only here to help Sakura and Tia choose underwear today.
If the Einzbern group had come along too, who knew what sort of hellish scene this place would have turned into.
Now all he had to do was patiently wait for the sales clerk to find the right sizes for Sakura and Tia. Then he could pay and go home...
"Good. Now come help me choose my underwear."
Huh?
Was he hearing things?
All Shirou had done was accompany his mother and his underclasswoman to a lingerie store. Surely that wasn't enough to give him auditory hallucinations.
"Don't ignore me, Shirou."
Rider hooked her arm through his.
The corner of Shirou's mouth twitched.
"......Rider, you're still here?"
"If you want to choose underwear, go ahead. I'm not some expert on women's lingerie."
Rider replied without expression. "A tall woman like me could never have boys fuss over her so gently the way they do Sakura, could she?"
"Urk."
"I'm not cute anyway. Shirou doesn't even want to help me choose underwear."
"That's not true. Rider is obviously beautiful!"
Shirou accidentally blurted out exactly what he thought.
A faint, triumphant curve appeared at the corner of Rider's lips.
"Since you think I'm beautiful, then please accompany me while I choose, Shirou."
With that, she linked arms with the boy like a lover and led him toward the counter.
Even if Rider's strength fell short of the Goddess of Creation, she was still a being far beyond humanity, one who stood among the highest ranks of Heroic Spirits.
Shirou had no room to resist.
...
...
What the hell happened?!
When Shirou came back to his senses, he found himself inside a single-person fitting room at the lingerie store.
The red-haired boy stood in the corner like a clothes rack, Rider's top and jeans draped over his arm.
Even folded up, the jeans still nearly reached the floor. Rider really did have incredibly long legs. She was already tall to begin with, and the proportion of her legs was downright ridiculous.
No, none of that mattered right now...
Why was Rider changing her underwear right in front of him?
And why was he inside the fitting room with her?
Shirou desperately tried to remember what had happened.
A few minutes earlier, he had forced himself to accompany Rider while she picked out some underwear.
He had thought that would be the end of it. Then Rider suddenly leaned close to his ear and whispered,
"Hey, Shirou... don't you want to see me wear it for you?"
"Huh?"
The enchantress from the Age of Gods smiled.
There was longing and temptation mixed into that expression, making it almost impossible to resist.
Little by little, Shirou's reason melted away.
Rider gently linked arms with him and led him into the women's fitting room.
Now, Rider was changing her underwear with her back turned to Shirou.
From where he stood, he couldn't see her from the front, but the view from behind was already more than alluring enough.
A bare, snow-white back framed by vivid, flowing hair.
A firm, full backside and long, shapely legs.
And...
"What do you think, Shirou?"
After finally changing into the new set, Rider turned around.
The single-person fitting room was extremely cramped, leaving the two of them practically face to face.
Shirou had thought he knew what to expect, but the sight of Rider in lingerie still surpassed his imagination.
Her purple hair cascaded down like a waterfall, gleaming with a dark luster beneath the fluorescent lights.
The delicate black-and-purple lingerie traced the curves of her voluptuous, provocative figure, somehow making her look both irresistibly seductive and strangely pure.
Lace patterns curled over her body like vines, standing out beautifully against her cool, pale skin and giving her an indescribably dangerous allure.
For once, Shirou felt the limits of human language.
"It's... beautiful."
"Hmph~"
Rider clearly wasn't satisfied with such a plain compliment, but the expression on Shirou's face was enough to leave her looking thoroughly pleased.
"Good. Let's try the next set."
"There's more?"
Only then did Shirou notice that Rider had brought four or five sets of lingerie into the fitting room.
"I'm going outside first."
Shirou hung Rider's jeans and clothes, still faintly warm from her body, back on the hooks and prepared to leave.
Then...
"Rider, are you in there?"
Sakura Matou's voice came from just outside the fitting room, separated from them by nothing more than a curtain.
"!"
Shirou and Rider looked at each other.
Even the cool and composed Rider had one or two things capable of rattling her. Sakura Matou happened to be one of them.
"W-what do we do, Shirou?!"
All of Rider's usual composure vanished. Cold sweat formed on her forehead as she looked to Shirou for help.
"Just say something to her first. She's going to get suspicious!"
Having plenty of experience with being caught in compromising situations, Shirou conveyed his instructions with his eyes.
Rider nodded.
"Ah... Sakura? Y-yes, it's me. I'm in here."
Stammering, she poked her head through the gap in the curtain.
"Wait...!"
The fitting room was simply too cramped.
And Rider was simply too tall.
So when one person leaned forward to stick her head outside, the other was forced back against the wall.
Rider's lace-covered, peach-shaped backside pressed firmly against Shirou.
Standing outside the fitting room, Sakura Matou asked, "Have you finished choosing your underwear, Rider? I want to see! Can I come in?"
"Not right now!"
Rider shouted without thinking.
The instant the words left her mouth, she realized she had reacted far too strongly and hurriedly clamped her mouth shut.
Sakura Matou tilted her head in confusion.
"Not right now...?"
With only her head and neck sticking outside while the curtain concealed the rest of her half-naked body, Rider hurried to explain.
"Sakura... that's not what I meant. I mean..."
"Not right now. I'm a little embarrassed... I'll wear it for you after we get home."
"Oh, I see. Then I'll look forward to it~ Hehe."
Seeing Sakura Matou smile at her without the slightest trace of suspicion filled Rider with a deep pang of guilt.
"Shirou... we can't lie to Sakura... We should tell her the truth..."
"Don't do anything stupid, Rider! If she finds us like this, we're dead!"
Shirou desperately tried to stop her.
Rider had no idea just how terrifying Sakura Matou could be when she was angry. That was the only reason she could suggest confessing so casually.
"..."
In the end, Rider gave up on telling Sakura Matou the truth.
Come to think of it, something had been pressing against her from behind for a while now...
Huh?
Rider suddenly realized what it was.
Her cheeks flushed, and she immediately became flustered and furious.
"Shirou! Don't do something like that with Sakura standing right there!"
Rider was panicking, but Shirou was even more frantic.
"It's not like I can control it! Who told you to have such a huge butt?! Stop pressing against me! And stop rubbing back and forth!"
"Guh... I'm terribly sorry for being a woman who's big everywhere!"
Rider ground her teeth and decided to get back at Shirou.
So she deliberately pushed back against him.
"Ugh!"
"What's wrong, Rider? Are you okay?" Sakura Matou asked worriedly.
"Ah, yes... I'm fine, Sakura." Rider forced an awkward smile.
"That's good. By the way, have you seen Senpai?"
Rider shook her head.
"Shi-Shirou...? No, I haven't seen him. Maybe he took the opportunity to run away?"
At that, Sakura Matou placed a hand under her chin and murmured, "That's strange..."
She had just asked the sales clerk, who told her that the red-haired boy was with Rider.