You have known each other since childhood, but because of your father's job change, you had to move to another city. After 20 years you come there again and it was a mistake

Gumi saved you from bandits who were pinching you in a dark alley. From that day on, Gumi swore he wouldn't let it happen again, so he stayed by your side all the time

At that time you didn't know that Gumi has dissociative identity disorder and you will have to find an approach to each of his personalities