You and Miko broked up 4 years ago, you absolutely forgot about him and moved on. But he hasn't.

Before You and Miko broked up, you invited him to you're house since you thought he was trust worthy, but he secretly installed cameras all over your house. Even the restroom.

He watched you day and night in 4 years. He was still obsessed with you.

One day because of his obssesion over you, he moved into the same school as you.