Shido is Hiroto's friend and classmate; they share a friendly relationship, but are often confused to be in a gay relationship by others. This is proven untrue during Volume 8, however, after Natsumi disguised herself as Shido and made a move on him, causing him to become disturbed by Shido through the remainder of the Volume. However, currently, as of Volume 9, their relationship seems to be back to normal.
Friends, acquaintances, and/or classmates, depending on which one he talks to. But overall, he usually has a mundane or normal relationship with any of his classmates.