For years, the government had kept a secret: there exists an alternate universe where mythical creatures such as centaurs, mermaids, harpies, and lamaias are real. Three years before the start of the story, the government revealed the existence of this universe and passed the "Interspecies Cultural Exchange Act". Since then, it has become possible for 2 people from different universes to temporarily merge into one being in one of their respective universes usually taking the appearance of the mythical creature (all mythical creatures are female) with the personality of the human (although they retain quite a few personality traits of the creature they merged with such as fashion, mannerisms, some likes/dislikes, and occasionally, relationship/sexual preferences). This merging has become required by some nations of the world to help improve relations with the other universe and help people from each universe explore the other universe.