Russel is a [saint] who was an expert in recovery magic. he was in a group with his childhood friends until the rest of the members learned recovery magic. Branded unnecessary and expelled from his group of friends, he meets a mysterious beauty named Sybilla. His infinite magical potential, combined with her guidance now allow him to reach heights once deemed impossible!

On her 12th birthday, Angele is infected with the strange and fatal disease that causes feathers to sprout from the body. She is sent to a solitary institution to be quarantined where she meets a man named Hakana and the wheels of fate begin to turn. (Source: Mangaupdates)
Based on the free game from Niconico.
Play the game in Japanese: https://game.nicovideo.jp/atsumaru/games/gm4581
Watch a playthrough with everything narrated: https://www.youtube.com/watch?v=wFmcgB3bikM