Aiko committed suicide for some reason, Honoka took her place because her father killed someone and went to jail, her mother ran away too.
Hanoka buried Aiko someplace deserted and was grieving her friend.
Then the absolute moron Kaito fucking strangled Honoka(Aiko) without asking questions, it's not like he could believe her anyway as she was an identical doppelganger, but took vigilante action and now he has a burden of killing an innocent childhood friend who suffered through parent misdeed.
What's worse, Kaito liked Honoka, he killed his love because she seemingly killed her friend?!?
Holy fuck. He better off himself because that's just the dumbest thing one can commit.