The incident was that one of the servants from Manji's father r*ped a boy from another shop, that's why Manji got sent to his uncle. His father hates gay people because his wife got mistreated by them, I believe. Though I mean a "normal" couple could have done the same thing. We don't know anything about the brothers and the mother could have definitely been some type of geisha. Maybe she wasn't popular with the customers just like Momo. But yeah there are still a lot of questions open regarding the family, Vol. 5 will not be the last one I believe, so maybe we get to know everybody's story later on. The brothers could be potential drama factors and Manji still didn't meet up with his mother, so still a lot of potential stories left.
I dont get it. I'll probably need to read it again but what's happening? What incident did he protect Manji from? Was the mum a geisha in the past? What other two brothers, that was never mentioned right? ....so confused.