Board Thread:General Discussion/@comment-27907368-20160323193924/@comment-27620479-20160607160937

Chara is the narrator, and they provide the music (and, of course, the soundtrack titles). Also, they don't just disappear after Frisk completes their journey. No, Chara is still there, as a literally soulless voice in Frisk's head, to plague their life with narration and incidental music. Of course, Frisk "fights back" by double-checking everything.