Mei Shindou is the adopted younger sister of Nikita Shindou, residing with him after both suffered the loss of their parents twice, leaving them deeply scarred by grief and emotionally vulnerable. She appears as a teenage girl with shoulder-length brown or orange hair, matching brown or orange eyes, a slim frame, pale skin, and a bust measurement of 89cm. Her wardrobe consists of casual outfits like hoodies, t-shirts, and miniskirts.

Personality-wise, Mei radiates honesty, innocence, curiosity, and a sweet deredere disposition, yet these coexist with intense jealousy, a brother complex toward Nikita, and moments of naivete. She often exaggerates situations and exhibits finicky eating habits. Her terror of drifting apart from Nikita fuels relentless efforts to reclaim his attention and affection, deploying tactics like cosplay with full commitment despite minimal success.

Romantic feelings for Nikita blossom during their cohabitation, though he remains oblivious until another character intervenes. Mei actively competes for his affection against another foster sister, channeling persistent and occasionally desperate emotional investments into this rivalry, with her endeavors continuing unresolved.