MC is apart of a special tribe completely composed of men whose first sexual encounter determines their sex, as tradition they annually host a tournament where the loser is chosen to be bride/sacrifice for a neighbor tribe in order for there to continue to be peace between them. The ML is from the neighboring tribe who also have special characteristics in the fact that the tribe members with the strongest/potent blood such as the leaders, are able to morph into shark men. The MC & ML end up eloping before his coming of age tournament when the ML gets injured and his blood that has aphrodisiac side effects, influences the MC and the ML in return for him having a long unrequited love for him.
Samezoku e no sasagemono