Kisaragi Mio

The "real" Kisaragi Mio from Kazatsugahama and Yuuma's real childhood friend. After her parents were murdered, she met Yuuma. However, when she and Yuuma went to Arashiyama-sou to solve Yuuma's memory issues, she accidentally ended up in a parallel universe, where her parents are still alive. The Mio from the parallel universe agreed to switch worlds for one week, so that Mio could spend some more time with her parents. However after one week, the "watashi" Mio never let the other (current) Mio return, until she avenged her real parents' deaths.