RWBY: Detective Pikachu

When she was young, Ruby Rose had a friend named (Y/N) (L/N). They were close friends, and even started dating. However, they had different visions of their futures: (Y/N) wanted to be a detective, and Ruby wanted to be a huntress, which led to the lovers splitting apart to follow their dreams.

Years later, Ruby is informed of (Y/N)'s death in Atlas. She heads over to his home to sort things out, where she meets a friendly Grimm called Pikachu. He has amnesia, and only she can understand him.

She learns Pikachu was (Y/N)'s pet, and he learns she is (Y/N)'s old girlfriend, and the two, believing (Y/N) is still alive, begin an investigation to find out what happened to (Y/N), what happened to Pikachu's memory, and what this strange R serum is.