Also, we have to take into account we don't know who Endo's informant is, for all we know it's someone in the city (Bankoku-Gai) or even inside of Red Chanpuru or works with them and they gave him the sanitised or biased version of the story, thus Endo decided they were like Furin, even though he's the worst judge of character. I'm not trusting this info, I'm sorry, why are people even taking Endo at face-value, he's a son of a bitch and a manipulative little shit with a very weird set of morals.
I do believe Red Chanpuru saved Suo from something, saw potential or Suo saw something he shouldn't and was taken in to keep him from running his mouth, he probably defied them at some point and that's how he lost the eye right when he was starting middle school. Mind you this kid was going to middle school in Makochi 2 hours away pre-Furin reform, I very much doubt Makochi was that interesting to that multicultural melting pot of a city that sounds like it is very closed to the outside (what if they're not allowed to leave the city, protection can turn into control over so many generations)
And also, if Red Chanpuru was really all about that idilic society, who exactly are they "protecting" the city from, why is Suo that familiarised with Red light districts... You guys have to admit this is sketchy as hell.
This sounds like it's become sectarian overtime and also, like they might be a gang turning into a crime syndicate.
If Red Chanpuru was really all that good, why would Suo look like that during the confrontation with Nirei, why would he go so far for Furin, for Sakura, why not just say he had to leave the country, make something up, why does he look so miserable at their headquarters
Why have this expression, that's not just someone who doesn't want to leave a group of friends
why was all of this necessary, if not to keep his friends as far away from Red Chanpuru as possible
Why those expressions and that much understanding
He really did consider himself part of furin (Endo does actually remember this so he might actually be insisting s bit on Suo not being his ally because he knows there was something and it will anger Sakura)
Why look like this now, dead inside, forced smile... Almost on the edge of breaking
Things are suspicious as hell