Tooru Saotome graduated from Yuei High School with the best grades, and came to Italy because of a mission. From then on, the story of falling in love and killing each other began.
The heroine is Midoriya Little Angel's senior classmate from the previous year, the grade from which Teacher Aizawa expelled the whole class. The heroine was originally from Class A, but because she went to the wrong place at the beginning of school, she escaped being expelled but was transferred to Class B (there were 21 people in Class B in that first year).
The story begins on a timeline where the heroine graduates, All Might and Andvar retire, and the little angels are in third grade.