Also known as: 平行世界, 平行宇宙, undertaleAU
Used for hypothetical, non-canonical situations, such as exploring the implications of a deceased character still being alive (a.k.a. what ifs, WIs or alternate timelines) or a radical shift in setting like fantasy to urban (a.k.a. alternate universes, AUs). Some copyrights such as Undertale and OMORI are notable for having a large amount of fanmade AUs.