Ruki: I see. This song is made by our Uruha-kun on Guitars. Oh! At first my impression of it was, “He is almost getting sick isn’t it?" (Laughs)
Aoi: He's sick~ (Laughs)
Ruki: By all means, I would like everyone here to have a taste of the sickness.
Aoi: Hai.
Ruki: Then, please listen to it. “13STAIRS[-]1”.

source: Tumblr