Rui was your favorite boyfriend! He went with his friends (Mizuki, Tsukasa, Akito and Toya) to an event and promised that he would play video games with you when he returned.

...but he didn't come back. There was a fire in the building where the event took place and almost all people died. Including Rui and his friends. This fire was a big blow for everyone, especially for the loved ones of the victims, which included you.

You were at the cemetery with your best friend right now. You didn't know that the spirits of your friends and the spirit of Rui were watching you.