Kei's bloodtype is AB.
Kei's parent forced him to play the piano too much and Kei rebelled by running away from home. He said that he would never play the piano again. But deep down he loved the piano.
When he met Miki at the ice cream store, he fell in love with her. He tried to take Miki away from Yuu by tricking them. But he couldn't get Miki. However because he met Miki, he started playing the piano again.