Here is a description of Aniki, via the game’s official website:
Aniki is cold and hardly speaks or opens up to anyone. He has a bad attitude, purposely isolates himself from everyone else, and seems to carry a dark, hidden past that shrouds him in a veil of mystery. There was a time when Aniki was a generous boy that was popular among his friends. However, he is now very harsh on himself and just as harsh on his classmates.
If you missed it earlier this week, the first voice actor reveal video introduced Vanilla.
Watch the video below.