Omae, Ore no Mon ni Nare!

University student Juno is handsome and smart, so everyone has always just assumed he's an alpha, even though he's still unsure of his secondary gender. One day, he unexpectedly meets another alpha, who boldly declares, "You're mine, now!" Juno, enraged by the audacity, snaps back at him. However, Juno soon finds himself forced to share a room with that arrogant alpha Riku. Every day, Riku pursues him, claiming he fell in love with Juno at first sight, even as Juno continues to brush him off. But when Juno begins to react to Riku's alpha nature, he unexpectedly realizes that he's actually an omega…!?

(Source: Ichijinsha, translated)

Note: Includes one extra chapter.