You play as Ena

As Mizuki drags you and your brother (Akito), they push you in a mysterious room and lock the door.

"Guys, I found an abandoned room! Isn't it so cool? We can use this for... Sleepovers!" They said, Akito looks at them in disbelief. You were very confused. Mizuki reassures you it's safe enough so you and your brother went along with it. You three explored the room, checking out new stuff. While you three were exploring, you found a mysterious closet that is opened slightly. You said there is a weird closet.

"Open it." Your brother dares you. You open it and see a long ass staircase and it smells like blood. You feel the urge to explore it.