Katakoi × Alliance

Akito fell in love the moment he saw Kiriya, a part-time math instructor, while on the school's rooftop. Even though they have never talked, Akito looks forward to every time he can spy on Kiriya from the rooftop. One day when Akito sees Kiriya, Akito rushes in to see why this math teacher is crying alone. In a panic, Akito asks Kiriya to teach him math. As they spend more time together, Akito realizes Kiriya is in love with another teacher at their school. Akito refuses to give up on Kiriya, though, and proposes they enter a One-sided Love x Alliance!
(Source: Futekiya)
Includes an extra.