Warau Hebi to Niramu Inu

Inui Rei changes his image after transferring schools and is treated like a "cool prince." But inside, he's a timid person who's still haunted by his past of being teased, and he's more afraid of people finding out about his past self than anything else. The one who keeps bothering Rei is Oomi Hiroto, a cheerful and friendly popular guy in his class. Rei doesn't like him, but for some reason, he won't let him go. And what's more, Hiroto threatens him with a "dark past photo" of Rei...! "Be my dog (pet) for a month." To keep his secret, Rei accepts the humiliating condition. However, Hiroto's "training" is sweeter and closer than he expected, and he's completely in control of the situation. In the midst of all this, when Hiroto sees Rei on the verge of breaking down at his limit, he...!?