As Izuku was dating Ochako his parents didn't trust her not one bit so they decided to force him to date another girl by who was also in a relationship but due to them both being forced they were told not to say anything about their relationship. One day they both saw that their lover are cheating on them with each other and they both decided to keep their arrange marriage as they have each other a chance (trust me they are friends they don't hate each other it was just both of their parents came together due to their ex lover)
Ship
Izuku x Momo