uke tried to search for his search love, thus despite being an Omega, he enrolled into a whole Alpha class, and all of the Alphas can't resist the urge for him, including his first love.
His first love only vagugely remebered about his childhood when he shared love with a little boy but then he moved way without telling him . And now he's drive by the lust for the Omega in front of him.
A little bit heartwrenching.
Sayonara Koibito, Mata Kite Tomodachi