Ore ga Ω de Omae ga α

Overview

Hotaru, a popular and talented student at school, grew up with his close childhood friend Takaya. He always thought that, when they came of age, he would awaken as an Alpha and Takaya as an Omega, so they could become mates and get married. But one day, Hotaru suddenly experiences his first heat! Shocked to discover that he’s actually an Omega while Takaya is an Alpha, Hotaru struggles to accept the revelation. As Takaya, drawn by Hotaru’s pheromones, approaches him with undeniable desire, Hotaru tries to resist, but he's unable to suppress the instinctive pleasure his body craves…!? (Source: Kadokawa, translated) Note: Includes one extra chapter.

Source: AniList