As I understand it, this gear can "boost" literally anything, not just multiply powers.
So I think it went like this—Issei did something cool that caused positive emotions and feelings in a girl.
Take his stunts at Rias's wedding, which made Rias fall for him, though I think there were preconditions earlier, at the actual Rating Game against Phenex.
So, a feeling arose, and since Issei wanted, no, WANTED such a girl to fall in love with him, the gear activated and that feeling was amplified, then again and again, turning simple fleeting admiration for an action and sympathy into mania and obsession!
Because if you think about Rias, Issei is the same as Riser, just hasn't fulfilled his dream yet.
But Rias hates Riser while loving Issei to distraction.
And with Koneko and Akeno the situation is similar.
Like, didn't Kiba say exactly the same thing to them that Issei blurted out, making them fall for him?
I think Kiba also didn't care about Akeno's nature, and told her that fallen angels are fallen angels, and Akeno is Akeno.
But somehow Akeno didn't chase after Kiba or anyone else, didn't try to give herself at every opportunity.
But she chased after Issei and tried to give herself!
So no need to worry that Issei won't be able to hook up with Koneko because she won't get psychological trauma—there'll be a moment!
And Kuroka will jump him as soon as she learns he's the Boosted Gear bearer.
She probably has long had hang-ups about kittens from the strongest, or they'll appear soon.
So you can breathe a sigh of relief—canon will live!
"So you're our 'master'?" Kuroka asked with challenge and mockery when Zeoticus left the room, leaving me to get acquainted with "my" pets.
That she didn't ask this in front of Zeoticus and was all modesty and compliance with him says she has brains and some sense of self-preservation.
But apparently this didn't extend to me.
"The master here is Lord Zeoticus Gremory, and I'll just look after you... like feed you, give you water, empty the litter box."
"..." Kuroka went into a stupor for a couple seconds, either from my words or from the tone and emotional content.
Well yeah, "deadpan" mode activated!
Though I hadn't turned it off, it just glitched from too big a shock.
"WHAT LITTER BOX?! Little pervert!" Kuroka blushed.
And apparently what made her mad wasn't the comparison to an animal but something else... so who's the pervert here?
Generally I don't understand these Japanese hang-ups about girls' pee and shit... as far as I'm concerned—shit doesn't stop being shit just because it came out of a cute girl, but the Japanese and accordingly local demons and yokai, which Kuroka is, a nekomata after all, think otherwise.
"The most ordinary litter box." I didn't even raise an eyebrow at her words, and didn't react to the slap either.
I didn't even feel the latter since I drank another potion that turns off pain.
No, I didn't foresee anything like this, and physical force isn't used on me, I just drank it to deal with another potion's side effects.
Even before me, Ren invented a potion for sharpening perception and improving memory.
What you study under this potion is permanently imprinted in memory, but you had to pay with a couple days of severe headaches.
Though after these two potions you had to drink one more for detoxifying the body, and use it no more than once every couple weeks, otherwise even a demon's liver and kidneys would fail.
Yesterday I was memorizing useful information for my specialty, since there are books here Ren only heard about in footnotes in other books and drooled over, so having gotten access to them I used it fully.
And I also memorized names and information on ALL the servants in House Gremory, which I also consider useful.
After all, I have pretty warm relations with the maids.
First, they remember my mother, second, I communicate with them as equals, more precisely even with respect, and I'm more emotional, though the latter is a mask.
This behavior knocked Kuroka and Koneko out of their stride.
Though you could see Kuroka was already ready to start apologizing for her rash and harsh actions.
I think they explained to her that they hadn't landed in a fairy tale and what would happen to them if they didn't behave appropriately.
If it weren't so and they were being sold to me as friends, like they'll do with Rias, Zeoticus wouldn't have said "they're yours now," and Kuroka wouldn't have talked about a "master."
Not giving Kuroka time to recover from the new shock, I continued.
"Also I don't recommend insulting or using physical force on other house residents, especially Rias Gremory-sama. This could lead to very bad consequences."
"So insulting you is okay?"
"Not advisable, Lord Zeoticus might not take it very well, and things will be very bad for you."
"Who the hell are you anyway?!"
"Lord Zeoticus Gremory's bastard—Ren, nice to meet you."
"Kuroka!" Kuroka introduced herself almost automatically. "And this is Shirone, my younger sister."
"Oh! Thanks for clarifying, otherwise I thought she was the older one!"
At my words, said just as emotionlessly with the face of an "ordinary brick," Kuroka's eye twitched.
"And why's that?" Kuroka scowled, while Koneko—or as she's now and probably forever will be called Shirone—perked up her ears.
"She's silent and listening carefully, not asking stupid questions or making rash statements or rash actions, which means she's smarter, more experienced, and therefore older!"
"0_0..." Kuroka was flabbergasted by my proof.
Shirone hid behind her sister and giggled quietly.
But Kuroka didn't stay in a stupor long.
"Kid, you saying I'm stupid?!"
"Hm?" I pretended to think, though my expression didn't change, but I managed to parody thoughtfulness. "Now that you, the Big one, pointed it out, it seems it really is so."
"Big? You saying I'm FAT?!"
"Hm?"
Logically, more precisely considering my plan to make a first impression that both nekomata would associate with the phrase—weirdo with an "M", I should've answered without thinking—yes.
But with that sunken stomach and ribs showing, you could see they'd seriously underfed for a long time and didn't have not just excess but necessary fat in their bodies.
So my tongue just won't turn to say that, since an insult should hit where it hurts, but here it'd be a miss!
"No, you're scrawny and tall... two heads taller than me, and like twice as old... hm... maybe it's more correct to address you as auntie?"
"Grrr! I'm gonna strangle you right now, Squirt!"
Making characteristic hand motions, Kuroka took a couple steps toward me to Shirone's ringing laughter.
Hm... did I miscalculate?
What if canon decides to take over and brand Kuroka a criminal for my murder?