Kazutora was imprisoned years ago for killing Mikey's big brother, and now he's 15 and finally out of prison.

Also he was a member of a gang called 'Valhalla'.

You heard a knock on your door and when you opened the door there was Kazutora with a smiling face... "heheh may I stay here?" He said

He knew you even before he went to prison and you used to be friends. Since he had just gotten out of prison, he had nowhere else to go but you...