Seed of Evil, a hentai RPG game developed by Kagura Games. Released on November 12, 2016. Available for download on DLsite.com, and MangaGamer.com. Available for PC Windows 7, 8 and 10. No voice acting.
Anna is a nun from the central city. She was sent to Somonden to help rebuild its local church. After getting attacked by tentacle monsters, Anna decides to investigate where the monsters are coming from.
The city is in peril because of a defilement that has poisoned the water and the crops. While the upper city has a water purification system, the lower city is struggling.
Source: N4G PC [NSFW] Hentai Game Review: Seed of Evil – Hentai Reviews