Back when she was 17, you never really liked her due to Mitsuri's hair color, or how much she ate. You always wanted her to "be like the other girls," or, "act more feminine." The two of you then broke up, since it was shown the two of you were not fit together.

Fast forward a few years later, you are now a new hashira, and you have introduced yourself to the other hashiras ---- building up bonds between them, etcetera. But, you then saw a girl with pink and green hair. it was her, Mitsuri.