Amazing as always!
This part is for his closest friends and past.
Kirijo Mitsuru
Aki and Mitsuru have been friends since middle school. She recruited him into SEES by having the evoker look like a gun. He thought it was interesting. She also seems to have him wrapped around her finger. Aki may complain about things but Mitsuru keeps him in check. She can get icy with him but never hurtful. In fact these two fight like a married couple. They understand each other and have each other’s backs. Next to Shinji, I'd say Mitsuru is his best friend. He tries to complain and get out of things like studying but she threatens and he straightens up. It's interesting to see them. He tries to support her after her father dies but he is at a loss and isn't sure what to do. I think just knowing that Aki is there for her is enough for her. He always defends her against Yukari when she gets talking about the past.
Aragaki Shinjiro
Shinji and Aki have a love/hate relationship. They grew up together. When the orphanage caught fire and Miki got trapped. Aki was held back by adults while he stood there not knowing what it do. I don't think Aki ever held Shinji responsible for that. Not like he did himself. While Shinji blames himself for the death of another woman, Aki blames himself for Miki. They have this in common and are always yelling at each other for it. "You never change", "Always holding onto the past" are some things they say to each other. These two are two peas in a pod. Aki shows great concern for Shinji when he finds out that he is taking special medication called "suppressants". And Aki hits him for it. He is always trying to get Shinji to come back to SEES but is always refused until Ken joins. They generally eat at Hagakure together and get along unless the past, persona, SEES or anything related is mentioned. They fight like brothers.
Amada Ken
Ken is a big source of pain for Akihiko because the events that took place earlier. During a mission Shinji's persona went berserk and killed Ken's mother. It's put a strain on the already strained relationship between Akihiko and Shinji. Akihiko doesn't hate Ken, he tries to look out for him as much as he can. Due to Shinji's last words Akihiko looks after Ken. Aki treats Ken kind of like a little brother, I think that's because of Miki and Shinji. I'm not sure what happens to Ken after the dorm closes but I like to think Aki looks after him. In FES, when it's time to choose the past or present, Aki sides with Ken. They choose the present, to continue without their friends and loved ones they lost. They learned a lot from them and they do love them but to change the past just didn't seem right. Yukari tells and belittles the two for their choice. Nonetheless Aki and Ken stick to it and fight for that choice.