User blog comment:AustinDR/Happy Sugar Life (Review)/@comment-27960787-20180727225446/@comment-2175012-20180727233708

Satou kidnapped an underage girl, killed the original owner of the apartment flat she shares with Shio; haven't read the manga yet, but I do know she also murdered her best friend after she discovered Shio.

As for other characters thus far, there was the manager of that one restaurant Satou decided to work at; she kidnapped and raped one of her employees but that is it. There's Satou's teacher, but he doesn't do anything heinous other than lust after women despite already being married; in the manga, there's Shio's and Asahi's father who abused them badly (such as him threatening to rip off Asahi's fingernails) and raped his wife when she accidentally pushed him.