Shimamura Hougetsu is a high school student known for skipping class, leading to her first encounter with Adachi Sakura on the gymnasium's second floor, which sparks their developing relationship.

Shimamura sports waist-length hair, initially dyed brown but later returning to its natural shade as she stops coloring it; she uses clips to keep hair off one side of her face. Her eyes are brown, though portrayed as purple in the anime. She has a slim figure yet acknowledges being out of shape despite prior basketball experience in middle school. She is shorter than Adachi, a fact she notes self-consciously.

Her personality blends laziness, airheadedness, and a pragmatic view of relationships. She considers social interactions bothersome and avoids deep emotional investments, believing most friendships dissolve naturally over time. This stems from childhood: once more outgoing, she became disillusioned after quasi-friendships ended when middle school classmates changed. Her elementary school bond with Tarumi deteriorated due to separation in junior high, where Tarumi gained a delinquent reputation. Shimamura reconnects with Tarumi in high school but remains emotionally guarded.

This reluctance makes her bond with Adachi significant. She perceives them as "birds of a feather" due to mutual disinterest in socializing, though Shimamura's detachment contrasts with Adachi's intensity. Shimamura frequently teases Adachi, reflecting her mother's mischievous trait, but tempers this with consideration—like withholding her preference for expensive chocolate to prevent Adachi overspending. She dislikes her surname for its clothing brand association and prefers the hypothetical "Shimazaki."

Shimamura demonstrates gradual development. Early on, she prioritizes convenience, nicknaming classmates rather than learning real names and initially ignoring Adachi's distress during estrangement. A turning point comes when she recognizes the value of sustained bonds, especially with Adachi. After Adachi confesses during their second-year summer break, Shimamura calmly agrees to date her. Later, she experiences a love epiphany realizing deeper feelings. She commits fully, confessing her love during their second Christmas together.

Her background includes a close childhood bond with Gon, her grandparents' dog, whom she compared to Adachi for shared loyalty. She maintains a "cool big sister" dynamic with her younger sister, playing video games together, though she questions if her care stems from duty or genuine affection. Her home life involves a mother who playfully embarrasses her and favors others.

As adults, Shimamura and Adachi maintain a long-term partnership, living together and vacationing jointly. Shimamura insists on financial equality, refusing Adachi's offer to cover vacation costs to avoid dependency. She also expands Adachi's social circle over time. A supernatural element reveals Shimamura once promised the ageless entity Yashiro to ensure she and Adachi reunite across lifetimes; Yashiro facilitates their meetings through reincarnations millennia later.

Her character arc centers on overcoming emotional passivity. Initially dismissing relationships as transient, she grows to cherish irreplaceable connections, actively working to sustain them despite her natural inclination toward detachment. This evolution defines her journey.