Veil Blue To Kuchinashi No Hanataba summary:

Mugi Hinata has had a physical relationship with Suku Oumi, a popular professional Go player, since their school days. They can only meet when in heat and have yet to become lovers. Even so, they are happy just to be together. Then one day, he witnesses shocking news about Oumi...? High-spec Go player α × Servile bookshop clerk Ω, an Omegaverse that is sure to swoon you.