Taisuke Sawanaga attends Sakakino High School after transferring from Aoi Gakuen. He is the younger brother of Miki Sawanaga and the second child of Mrs. Sawanaga and Ayumu Inou, unaware of his biological father within a complex family structure featuring numerous paternal extended relatives. Standing 171.6 cm tall with brown hair and teal eyes, he ranks among the tallest in his peer group. He typically wears his school uniform, casual grey shirts with blue pants, or a red speedo for swimming. His personality mixes boisterous humor, overt perversion, and sporadic thoughtfulness. Frequently comic relief due to exaggerated reactions to romantic misfortunes, he openly ogles female classmates. Despite his generally good-natured role as Makoto Itou's best friend, he burns with envy over Makoto's popularity with girls. Taisuke exhibits persistent romantic ineptitude and poor boundary understanding. He doggedly pursues Kotonoha Katsura despite her clear rejections and disinterest, failing to impress her—a pattern repeating with others like Hikari Kuroda, who carries unreciprocated feelings for him. His middle school crush on a girl surnamed Mori ended when she dated another boy, deepening his romantic frustrations. Controversy surrounds his interactions with female characters, showing a tendency toward coercive behavior. He pressures girlfriends into sexual situations while failing to recognize their reluctance or distress, including non-consensual encounters with Kotonoha and Sekai Saionji, sometimes influenced by third-party misinformation like Otome Katou's. These actions stem from an inability to interpret emotional cues, not malice, operating under a misguided belief that forcefulness constitutes romantic initiative—though he respects breakups if initiated by the girlfriend. His narrative role shifts across adaptations. In the visual novel, he dates Sekai or Kotonoha depending on Makoto's choices, with both relationships ending when the girls return to Makoto. The manga portrays overt lechery and hints at bisexuality through flirtatious behavior toward Makoto. The "Valentine Days" OVA focuses on his desire for Valentine's chocolates while observing girls compete to gift Makoto. Despite his flaws, Taisuke displays occasional perceptiveness about others' relationships. He advises Makoto to commit decisively to avoid hurting Kotonoha or Sekai and reassures Kotonoha to respect Makoto's choices, potentially preventing destructive outcomes. His dynamic with Hikari features moments of cooperation, like participating in a beach watermelon-smashing contest and agreeing to attend a school dance together, though Hikari often dominates their interactions.