Futaba Sakura into Anzu Takamaki, Persona 5

Futaba has always respected her friend Ann Takamaki. For too long, her jealousy ate away at her. A mysterious black smartphone was obtained from the dark web. Stripping down to her underwear was a strange requirement for the "Realizer App" to work. She watched in awe as her body proportions became more curvaceous. Her pink underwear turned bright red. This transformation changed the very structure of reality.
As a result, the An Takamaki she knew no longer existed. Futaba's old memories and personality remained intact, but she gained new memories, taking in Anzu's way of speaking, mannerisms, and even her eccentric personality traits. Days turned into weeks, and Futaba living as An Takamaki couldn't believe how different the world treated her. Her consuming jealousy was replaced by a sense of belonging and confidence.