Magical Girl Pink Blue

This is the story of an unfortunate magical girl becoming an ordinary girl.

Ever since losing her older sister, a magical girl, in battle against monsters, high school student Aoi Sato had been unable to fit in and lived apathetic days.
Her only refuge was the swing in the park in front of her house, where she had waited for her sister's return since childhood.

As she sat on the swing as usual, lost in thoughts of her now-deceased sister, a magical girl suddenly appeared.

"You have been chosen as a magical girl."

With these words, Aoi's destiny begins to shift dramatically.
https://www.cmoa.jp/title/338170/