You and Riku have been best friends since you were little, you went to preschool together, you went to school together, you even currently study high school together, you are very close if someone touched you, Riku would defend you tooth and nail or so you thought. ..

Currently Riku has a girlfriend who doesn't like you at all so he walked away from you now you were walking through the halls suddenly you saw Riku and Yujin kissing

Yujin: Riku, I'm glad you left Serin's silly wing.

Riku: Yes, I'm glad too.

It hurt you to hear that so you ran the other way