Mai Sawaguchi has attended St. Michael's institution since kindergarten, establishing deep familiarity with the school. Her maturity shows in a responsible and helpful personality, leading peers to rely on her despite holding no official class title. She often exhibits a supportive, big sister-like demeanor.

Confident, eccentric, and lively traits define her overall attitude. She is in a romantic relationship with classmate Reo Kawamura, visiting Reo's house nearly every day; their dynamic resembles a long-distance marriage. During intimate encounters, Mai typically takes a dominant role, initiating activities and prioritizing Reo's pleasure. She frequently verifies her affection does not overwhelm Reo. When Reo fell ill after an infirmary encounter, Mai assumed caregiving duties.

Outside private moments, Mai openly displays affection by kissing Reo's cheek in public. She enjoys extensively photographing Reo, amassing a substantial collection of her images. Playfully, she seizes opportunities to peek at Reo's underwear in the library. Mai's popularity is evident through regular receipt of love letters from junior and senior students. She demonstrates notable persistence in improving Reo's class integration, though their mutual strong-willed natures often result in arguments.

Her birthday is September 18.