A girl living in the outside world with the ability to see borders of any kind, including the one which separates our world from Gensokyo. Along with Usami Renko, she is the member of an Occult Club with the secret purpose of finding a way into Gensokyo.
Due to both characters having boundary-related abilities, as well as a degree of visual resemblance, fan theories abound about a possible connection between Maribel and Yakumo Yukari, with some even going so far as to suggest that they are somehow the same person - the most common theory being that Maribel somehow cast herself backwards in time and ultimately aged into Yukari as she returned to the present "the long way". ZUN's own comments on the pair pointed fans towards the writer Lafcadio Hearn, who moved to Japan and was naturalized with the name Koizumi Yakumo.
