The World Where I Belong is a Supernatural Webtoon Original created by GMOW; it updates every Wednesday.
A high school student's attempt to end his life is interrupted by a strange girl with even stranger powers.
Kouki is the main character of TWWIB, and he is the character that attempts to commit suicide. He is stopped by a young girl named C. Airi who calls herself a savior. It is mentioned that he used to be more open in the past, but it seems some events happened to make him as disclosed as he is.
C. Airi is a savior assigned to Kouki to stop him from committing suicide. Her physical form is a flock of red and blackbirds. When she's in her "human" form, that is called her ethereal form.