Responses
I think it might be related to drugs, too.
Maybe the dealers are using the orphan kids as drug mules. The kids won’t understand what’s going on other than members of Red Chanpuru, people who they trust and look up to, told them to do it
My guess Red Chanpuru is becoming what Furin used to be but worse. We already know that they’re basically like Furin, protectors of their town, but more dangerous. If Rakta is saying Red Chanpuru is a poison, then it’s possible that there’s corruption in the group and it’s slowly taking over. With every new kid joining, it’s easy for the bad ones to slip by without notice. It’s possible the first step for those with malicious intentions is to take over Red Chanpuru and the town, then move onto other groups and their territories, Furin and Makochi being one of the targets. Suo/Sun Fei probably heard about the plans and is trying to stop it before it could reach his friends.
Another theory could be the group is currently leaderless and different fractions within the group is fighting to become the new leaders. One fraction could be the corrupt members who want to turn Red Chanpuru into something similar to what Furin used be like, while the other fraction (Suo/Sun Fei is definitely in this fraction) is fighting to keep Red Chanpuru the way it is. Suo/Sun Fei probably went to Furin to see if they could help, but things become complicated and dangerous so he had no choice but return, leaving everyone behind