Right, because Marisa used to be a resident of the Human Village, if she becomes a youkai Reimu would have to kill her. This is only prolonging the inevitable tough, it's obvious that Marisa would become a youkai eventually, one way or another. Probably not in the main series though.
Actually, what if one of the reasons Marisa is researching an immortality potion is so Reimu can't kill her?
last edited at Feb 7, 2025 1:58PM