Shishi Jin No saiAi (Kadokawa Ruby Bunko)

[Machine Translation] Noah, a sorcerer who lives alone deep in the forest, rescues an injured beastman child. One night, while living with the child, who has lost his memory, Noah names him Rei, and is embraced by Rei, who has suddenly grown into a young man. Moreover, when he regains his memory, he discovers that Rey is a prince of the beastmen's country. He tells Noah that he was attacked by his enemies as his brother's shadow warrior, that he was transformed into a child by magic, and that last night he embraced Noah because he could not control his mating impulses as a beastman. He also tells Noah that last night he embraced Noah because he could not control his lustful urges as a beast. Once you take a turn, you are bound to your partner in this tale of doomed love.

森の奥で一人きりで暮らす魔術師のノアは、ケガをした獣人の子供を助ける。しかし、記憶を失ったその子供にレイと名付け共に暮らしていたある夜、突然青年へと成長したレイに、ノアは抱かれてしまう。そのうえ、記憶を取り戻したレイが獣人の国の王子だったことが判明。兄の影武者として敵に襲われたこと、魔術で子供の姿に変わっていたこと、そして昨夜は獣人として発情期の衝動が抑えきれずノアを抱いたことを告げるレイ。「結婚してくれませんか」とレイに求婚されたノアだが...?一度でも番えば相手に縛られる、運命の恋物語。