Ninomiya Nagi

A wealthy transfer student senpai who turns out to be Hiroki's true fiancee: in fact, their parents decided to marry them when they were younger. Because of her strict father, she doesn't have a say in the matter. Nagi falls in love with a boy she met on the way to her fiancée house.

Spoiler

The boy is revealed to be Hiroki. Hiroki is Nagi's first love and later it is revealed that Nagi is Hiroki's first love.