[Crs (Shirasu)] Junketsu no Miko ga Ochiru made ~Shokushu Cli Zeme no Kairaku ni Oboreru | 直到贞洁的巫女堕落 ~沉溺于被触手折磨的快乐~ [Chinese] [莉赛特汉化组]

↓An interesting point of view of this story. Also the guy's first date's memory didn't survive with her reincarnations. So he's all stranger to her now.

Once upon a time the boy wanted to save the girl he loved (the saintess) from the church and failed. The girl's soul itself is fated to keep reincarnating as a saintess only to get used and sacrificed by the church. So the man who loves her sold his soul, his limbs, and part of his five senses to a demon. Since then he's been trying over and over to save her reincarnations from her sad fate but he's failed during every attempt until now. But the new problem is that it's been too long so his soul has been eroded by demonic energy and he's barely maintaining his sense of self at this point. A little bittersweet.