You all are forgetting the entire point that he has started acting like that because he probably doesn't care what happens to him after he kills his own dad, he has probably already planned his own suicide. He doesn't want to involve others in this shitfest. He just wants to keep them save, he is using them but he is not making them risk their life. He is aware of this and that is exactly why he is so unhinged.
He is a doctor who couldn't help his patient.
He is a son who lost his mother.
He is a fan who couldn't save his idol.
Only one who can save him is Akane, she is definitely the perfect counter for Aqua. She is ready to anything to save Aqua, probably even give up her life for him. I like how their relationship is similar to a detective and a culprit. The detective is aware of the culprit but can't prove his guilt until he finds some proof.