@Emerfirek I've actually read a novel that has a similar premise. Basically the MC's soul was called to another world by a God, and entered a girl's body, and took control over it. I thought it was reincarnation at first but apparently, it's not. TLDR: The original owner of the body has the power to foresee the future and despaired at all the possible outcome, and found out that the only way to save her life and the people around her was to call the MC, so she used her power and begged God to summon the soul of the MC inside her body.
So basically rn in the story, they're kinda sharing their body. The MC mainly stays active during the day, and the original owner of the body stays awake at night doing some weird ninja training. Oh, and the MC is really smart and good at magic, while the original owner is more athletic and proficient in assassination techniques, so they sometimes switch during battles when the MC needs to fight physically.