Yaoi with story

MC is an accidentally created doppelganger who needs to kill a human in order to live in his stead. It shouldn't be an issue, because the selected human is a murderer who deserves to die... But somehow, he doesn't seem like a bad person at all!

Kotone is a hardcore BL fan, but he always considered himself to be heterosexual. A deathly accident transports him to another world as the Chosen One of Nagi, a Sacred Beast. Nagi needs to spend a night with his summoned human in order to become more powerful, but Kotone isn't going to let that giant snake have his way with him!

When a summoning circle appears and Umehiko's sister gets pulled in, he takes quick action and sacrifices himself to save her. But now he has to serve the arrogant sorcerer Theodore as his Blessed Maiden, a human whose physical touch can restore the sorcerer's magic power. And the spell cast upon him makes it almost impossible for Umehiko to resist...