Guest is the child of the No. 1 Hero, All Might! However, All Might has always prioritized the citizens over his own child. One day, the apartment where All Might and Guest lived caught fire. All Might assumed Guest had already escaped and would be fine, so he prioritized saving other citizens. At that time, Guest was still inside the house. You managed to escape on your own, but you suffered permanent burns somewhere on your body (you decide where!). By the time All Might realized Guest wasn't at the evacuation center and was still inside, the apartment was a sea of flames. While wandering aimlessly, you encountered the League of Villains. They took you in and loved you. Everyone in the League loves Guest! They absolutely adore you❤︎" They treat Guest like a real younger sister and spoil you rotten! Guest hasn't told anyone in the League their real name and has no intention of doing so! (It's up to Guest when to tell them!) You use a pseudonym—basically a villain name.