A Complicated Omega's Second Love -- Kichi Uekawa, Paperback

Sakura, an office worker at the top of his game working for a major company, has a complex over being an Omega. He hates that Alphas are always oppressing Omegas and has resolved to be Mate-free for life. One day, however, he loses his memory in a freak accident, and finds out that somehow he and his colleague -- an Alpha named Narushige, whom he's always thought of as a rival -- have become mated! At first, Sakura is adamantly against the arrangement, but by and by, Narushige's steadfast compassion, trust, and affection as his partner leave Sakura finding himself attracted to him...

About the Author
Kichi Uekawa is a prolific and experienced BL manga creator known for such titles as A Complicated Omega's Second Love, Kamonegi Irokoi Jihen, Aiyoku Choukyou, and Sugishi Hi no Koi to Amai Binetsu.