Sei's onee-sama isn't given a name, and is only referred to as Rosa Gigantea. As a bouton, she chose Sei simply because she liked her face, but this later proved to be untrue when she later confessed that she only said it so that she wouldn't be a burden to her. Her last bit of advice to Sei before graduating was to not get so absorbed in people she treasures. And Sei, wanting to repay her onee-sama for her patience and kindness, is advised to pay it forward to her future little sister.
Relationship with SeiEdit
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