hi art! o7

here's a run-down of ibuki (not the full list):

• oni originally referred to ibuki's grandpa, and eventually became about him too

• ibuki calls himself the descendant of oni, likely because he is the "2nd generation of oni". the 1st generation is his grandpa. hence being a descendant!

• ibuki is mizusaba's younger brother, but ibuki is so respected and reliable in the community that he's everyone's "big brother", so even mizusaba calls him by an older brother naming

• it seems ibuki got interested to go to japan thanks to niceP's invitation. after arriving in japan and presumably meeting up with niceP (idol story 1), he somehow hears that crimpro got taken down by tetora, so he tries to go meet tetora to learn more about him

note: from here on is my own personal attempt to compile the events!! i'm talking based on my own understanding of the events

prior to supervillain and its events, the oni vigilante group and crimpro were enemies, and the oni group were the first people to go against crimpro and take them down. after defeating crimpro, the group disbands likely because the boss goes to the US. (this "went to the US" boss is very likely to be ibuki). this seems to have weakened the group since then (supersized villain ch5)

in idol story 2, ibuki doesn't fully confirm to tetora he's the boss, but based on the information we know and their dialogue in the story (boss went to the US, group had a descendant of oni), it should be him anyway? which means he was part of taking down crimpro the first time around.

by the time supervillain happens, crimpro revived itself, and became a LOT stronger than before because it fed on the okinawans' fear and hatred of ES. it became so strong in okinawa that even the members who were previously in the oni vigilante group joined crimpro. (supersized villain ch6)

this is the part that tetora mentions to ibuki! tetora seems to hold conflicting feelings about his decision to take down crimpro, and one of them is because he feels like he may have "a lot of unsettled business" (stella maris hidden island 2). while he's glad that the evil crimpro was defeated, he feels like he might have made people who weren't 100% evil suffer in the process (he mentions these conflicting thoughts in supervillain, supersized villain ch15), so it tends to weigh on his mind. this is shown in stella maris, where he constantly fidgets whenever he's reminded of his time as a spy for crimpro, and even says he sees it as his dark past.

so when tetora learns ibuki is the boss of the vigilante group, he wonders if ibuki's here to take revenge for hurting those vigilante members that later on joined crimpro. it's hard to tell ibuki's feelings on this as he just says he won't take revenge because it's old-fashioned... but after getting a chance to throw a deadly kick at tetora and seeing tetora dodge it, he seems to be satisfied that tetora is the real deal. hence saying "i'm sure even the guys at crimpro were happy to get taken down by you" (which implies even the vigilante members who joined crimpro were "happy" about it too!)

beyond this, i'm not sure haha. this is my own interpretation, but it seems like ibuki gave tetora a reason to have beef with him (throwing sneak attacks on tetora in a "villain-y" way?), while ibuki feels satisfied enough to know tetora is genuinely strong (and potentially even capable of "exterminating" him, the ogre?). in his introduction quote, ibuki says that "he'll be looking into things with his own eyes and confirming it for himself", so that adds up with how he acted with tetora!

what makes this a bit confusing is that the vigilante group seems to have been called "oni", and the boss himself was known as oni too because of his ancestry. this is again my own interpretation, but i assume the oni family (ibuki and ibuki's grandpa) was just that influential, that even a whole group led by one of them is called oni.

hopefully i didn't miss anything crucial. the lore is scattered across various chapters and stories, so it can be a bit tricky to compile. i hope this helps and let me know if you have any questions!!

stories i referenced: ibuki idol story 1, ibuki idol story 2, supervillain, stella maris, ibuki's introduction quote