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