He reached behind his back and pulled out a well made clip point Bowie knife. The whole blade was highly polished giving it the appearance of being brand new, which was fair seeing as it was only a couple of moths old and hadn't seen much use. On both the handle and blade were small sections that had been deeply inscribed and filled with gold that now looked to be a part of the weapon, all in the shape of various runes, "I made this a few months back for protection. The runes reinforce the enchantments meant to keep the edge sharp and undamaged."
Azazel made a show of leaning forward and squinting at the blade over the distance separating them. Seeing the ploy for what it was, a way to get him closer, Junichiro flicked his arm and launched the blade through the air to pierce the ground near Azazel's feet. He wasn't worried about losing the blade, it wouldn't do fuck all to protect him from Azazel anyway, so instead of getting closer to the fallen angel, he'd just gotten the knife closer.
Giving a little huff of amusement, Azazel picked up the knife and did give it a closer look, "Hmmmmm not too shabby. Decent craftsmanship. Useful, if somewhat weak, enchantments. Given your current limitations, this is rather good."
With a flick of his own wrist, Azazel returned the Bowie knife to Junichiro in the same manner he'd received it. Junichiro flinched as the blade buried itself tip first into the ground at his feet. He quickly retrieved it, cleaned the dirt off on his sleeve, and slipped it back into the sheath hidden under his shirt on his lower back, "If I had a larger mana reserve I could have done better. I'm limited by both my materials and my personal reserves of power."
Azazel shrugged uncaring, "I'll be sure to include common methods of expanding a mana core in the spell casting materials."
Junichiro blinked, "There are methods for that?"
"Oh yeah, quite a few. They have limitations, of course, and only work for human mages, but they can help a magical core grow a bit with dedication and some time. Most mages just ignore it though and only grow through exercising their cores with casting spells. It does take a fair amount of time for them to do all the calculations for each spell, and even longer to get good enough at them to cast the spell quickly."
Junichiro considered that and nodded his head. What he knew of DxD spell casting for humans was pretty limited, but he did remember they needed to do mathematical calculations of some sort. Something about doing the calculations to make their spell circles to cast their spells? He never really payed much attention to that as the Imagination Magic of devils was much more prevalent and interesting. Still, given how much math they needed to do for each spell, combined with the sheer amount of practice they must need to do it instantly, it made sense they used that practice as their main method of growing their cores instead of dedicating even more time to another pursuit for that purpose.
He, on the other hand, didn't care so much about actually casting spells. He wanted the primers so he could learn how it was done and possibly use the information in his work to make new things. What things? He had no idea. He didn't know nearly enough to even speculate beyond 'spell things'. Even so, that was no reason to ignore a possible avenue of research!
"Aside from enchanting, I can make single use spell scrolls. That's what the teleportation spell I tried to use was, a scroll." He gave Azazel a hairy eyeball, "That one scroll took me a long time and a lot of mana to make." He went back to giving Azazel a bland look, "It all depends on how powerful the spell I'm trying to put on the scroll is. Though, the teleport is about as powerful as I can get with just plain parchment. For the really potentially crazy shit, I'd need things like dragon skin, or angel feather quills, or kraken ink, stuff along those lines. You know, natural magical shit."
Azazel looked rather surprised, "Wait, you can put spells onto a piece of paper and then cast them? Isn't that just the talisman magic that lots of eastern human groups use?"
Junichiro dug into one of his expanded pouches and pulled out a rolled up piece of paper. He unrolled it so Azazel could see the weirdly drawn picture that looked vaguely humanoid, "Your art is crap kid."
Grumbling to himself, Junichiro sent a pulse of magic into the scroll. The scroll, and Junichiro, both vanished from sight after the Scroll of Invisibility was cast. Azazel let out a low whistle of appreciation, "Nifty trick against mundanes, but you're still pretty easy to detect."
"Yeah well, this is just meant to work for a short time as an emergency escape from mundane police."