He thought about that for a while and slowly began to smile. No one would consider a kitchen knife to be a weapon. Add to that how much people would be willing to pay for a knife they could use for decades and you had an attractive option. He could even mana forge it to make it sharper and more durable. As long as he didn't put an actual enchantment or runes on it, a supernatural creature would have to actually touch the knife to notice anything. Mana forged items didn't radiate magic, the mana was more... inactive? That wasn't the right word but it was close enough.
Okay so his plan was this. Spend the next five days forging kitchen knives out of abundantly available junk steel. Make them all mana forged to work on increasing his mana pool so he can make better stuff sooner. Sell said knives at the open air market on the weekends. Use the proceeds to buy a refillable prepaid credit card. Use said credit card to buy better materials off the internet. Use said materials to make better items to sell, maybe make a few Wands of Repair and diversify by selling repaired antiques. Rinse and repeat.
He could do that until he had the necessary items to protect himself. After which, he could head for... Tokyo? … No no, Kyoto. Yasaka's yokai faction was in Kyoto. As long as he had enough offensive, defensive, and escape magic items, it should be relatively safe to enter Kyoto and find a place to set up shop to sell magical trinkets. He highly doubted they would care about his age there.
That was the plan then. Prep here, head to Kyoto, work there, then maybe head to Kuoh when he was sixteen or seventeen. He was interested in joining Rias's peerage. It might seem contrived or a stupid thing to do, however he simply wanted to. He needed no other reason or excuse to do so.
Of course, it helped that doing so would put him into contact with many of the most powerful beings in the supernatural world. Beings he could likely find some way to scan and mimic. Not to mention all of the Sacred Gears that her peerage would encounter over time. Sacred Gears he could likely study, maybe even steal for himself. Speaking of, he was definitely going to steal Ddraig from Issei in a few years. He'd need to find someone else with a Sacred Gear to study first though. There was also the financial benefits and connections being attached to a pillar devil house would have. He had to wipe a bit of drool off of his lips just imagining the materials he could probably get through Rias.
So, yeah, he was pretty certain he would join Rias's peerage, become the next Red Dragon Emperor, and then open his own shop to sell awesome stuff. It seemed like a good plan to him.
Junichiro looked down at a collection of knives he'd spent the last five days working on. He'd made several different styles of kitchen knives such as gyuto, santoku, yanagiba, usuba, nakiri, and others. It wasn't too hard for him to make a top quality knife after he'd used runes on all the tools necessary. Mana forging was faster and easier than regular forging, files with rune work cut through hardened steel like butter and made shaping easy, and so many other little benefits of magical tools. Thanks to the ease of his work he now had three complete eight piece knife sets and a few extra gyuto, santoku, yanagiba, and nakiri knives on the side.
He had an example of each knife placed out for viewing on a wooden crate that contained the rest of his knives. The crate was on its side so he could reach into it easily. He made his pricing simple, each individual knife was priced at ten thousand yen, a set of eight was discounted to seventy thousand yen. Essentially, buy seven get the eighth free. Considering it had only taken him time and effort while his material costs were... nothing. It was pretty much pure profit. If he sold every last knife and knife set over the weekend, he stood to make four hundred and ten thousand yen.
Of course, knives weren't all he'd spent his time creating. He'd finally made his mana concealing amulet. It didn't actually hide his mana, that would be stupid since everyone had at least some mana. No, it took a reading of his mana pool when worn and 'locked' the aura of his mana to that level. As long as he wore the amulet his mana pool would appear to only be the tiniest bit bigger than any other random idiot on the streets. Which pretty much made him invisible to the supernatural as the small extra bit could be chalked up to good genes or an ancient mage ancestor. Nothing even remotely interesting or impressive.