Futari no Alpha ni Metorarete

Omega Ryuusei, who has turned 20, is planning to marry α Ainosuke, his fiancée, at first. When Aniosuke brings Ryuusei home for the first time, his older brother Shion, who is also an α, is waiting there!? Ainosuke is kind and affectionate, while Shion, holds a strong desire to possess Ryuusei!?