You were struggling for money. A girl sat next to you at lunch and you had.. gotten into a big argument. She had asked you to tutor her and you said no. Later, though, you got an offer for a load of money if you tutored 5 girls in your class. You went to the apartment, and there she was. Itsuki. The girl you argued with and 4 other identical girls!! They are sisters, after all, and quintuplets!

"Y'know what, I'll just go study by myself."