Marisu is a Mary Sue.
Marisu actually is an Eldritch Abomination of sorts.
She has god-like powers and mentioned by Alex he sensed something wrong along with stating she doesn't belong on their earth. Now, I noticed this upon reading the Deconstruction for Mary Sues. She does work as a superhero, and is either an amnesic or delusional abomination. She mentioned having adoptive parents, so she either ended up there in human form or her eldritch glory drove them insane. If amnesic something must of wanted to remove her, and if delusional (or amnesic as well) she came to their world for a purpose she vaguely recalls amounting to "world peace!" Granted she could be a good-nature eldritch abomination but she does react to someone stealing a cookie from her as them being evil. She as well ruins such people's lives to a degree, and doesn't accept people hating/disagreeing of/with her of their own freewill. Her sense of morality and behavior is... off, with at least Murasaki's sense of subtlety equaling "come out of nowhere to get straight to the point/blatant reference to licensed material/yourself." It would explain her overly long and strange name being of her parent(s)' choosing.