I don't think people like to talk about it, but I can understand why. [ He remembers watching Ichimatsu shift uncomfortably as he talked about it. ]

Sounds like some people were drugged in a way that changed their behavior, and there were some malicious aliens were allowed on board.

...A lot of people were hurt or killed. [ There were killings was what he heard, but somehow that sounds even uglier - like people were killing each other. Aoba's glad to leave that as the unspoken elephant in the room. ]