"No doubt she's a rose. But she's also a peony and a tiger lily."
I'll spare you the details and simply say that I'm the one who defeated Kasen Ibaraki.
Do you like history? I don't mean to brag, but I'm actually pretty famous.
They say that by eating the flesh of a hermit, a beast will turn into a beast youkai, and a youkai will gain significant strength. So, what would happen to a human? Would they turn into a youkai? If that were the case, then surely there'd be former humans among the youkai. My companions exterminated their share of youkai, but that may well have included some former humans.
Dragon extermination and oni extermination fall under the umbrella of youkai extermination, but I feel like they're unique. My companions and I once exterminated an uwabami youkai, but I suppose it was closer to a big snake than a dragon.
Oni extermination typically entails dishing out some form of punishment, as opposed to actual extermination, which would likely present quite a challenge. After all, the word "oni" derives from "onu," which means "not present."
The tale of me chopping off that oni's arm is quite well-known. I heard it's become a popular subject for plays. It seems the arm itself was left untouched somewhere in the Outside World (which, from what I gather, is what those here in Gensokyo call my world). Without getting too far into it, an oni's arms can be considered its true self. So even that one abandoned arm could've caused a fair amount of trouble.
I once used a large bewitched blade known as Onikirimaru. I believe there's a sword of the same name in the Outside World that's been passed down through the generations. Should you ever lay eyes on it, remember that it's nothing more than a sword forged from what remained of my shattered blade. My Onikirimaru was far longer, for if it hadn't been, I would've never managed to slice off that oni's arm. My sword shattered when it cut through the bone, and some fragments were lost, which is why the new Onikirimaru is shorter.
Of course, a shattered bewitched blade is still a bewitched blade, and the fragments can still be used to exterminate youkai and oni. Provided they're wielded by a brave enough warrior. Like me, for example.