Hina Hikawa is the younger twin sister of Sayo Hikawa and guitarist for the idol band Pastel*Palettes. She attends Keiho Women's University and was previously student council president at Haneoka Girls' High School. Her appearance features light teal shoulder-length hair with sections braided and tied with small yellow bows, sharp green eyes, and a casual style incorporating pants, shorts, and a gingham jacket worn around her waist. A natural genius blessed with exceptional memory and learning capabilities, Hina masters new skills rapidly—often after a single attempt—but quickly loses interest due to boredom. Her personality is cheerful, candid, and carefree, yet she struggles with social awareness, frequently failing to perceive others' emotions or contextual cues, leading to unintentional insensitivity or blunt remarks. She describes experiences using distinctive ideophones like "boppin'" (るん) and "pipi" (ピピッ), translated as "boppin'" and "zappin'" in English localizations. Hina harbors strong curiosity for unfamiliar concepts and people who differ from her, occasionally engaging in mischief or teasing bandmates, especially Aya, whose emotional reactions intrigue her. She prefers sweets, gum, and junk food, while disliking flavorless foods like tofu skins due to texture sensitivities. Her relationship with Sayo is central. Unlike Sayo, who initially resented their twin dynamic, Hina openly embraced it and persistently sought shared activities to bond. However, her effortless mastery of Sayo's hobbies exacerbated Sayo's inferiority complex and strained their interactions. Despite frequent arguments stemming from their contrasting personalities, Hina maintained unwavering support, attending Roselia's performances in disguise when explicitly asked not to. Over time, mutual understanding grew, leading to gradual reconciliation and warmer interactions. Hina began playing guitar after observing Sayo and later joined Pastel*Palettes by audition. She initially claimed band involvement was a diversion but gradually committed more seriously through Aya's encouragement. She admires each bandmate distinctly: Aya's perseverance, Chisato's composure, Maya's technical skill, and Eve's uniqueness. Pastel*Palettes transitioned from miming instruments to genuine performance after a pivotal incident, solidifying Hina's dedication to their collective identity as idols. Additional traits include fluency in English, high academic scores contrasted with difficulties interpreting map symbols, and a stated interest in volleyball. She was the sole member of Haneoka's Astronomy Club, colloquially dismissed as "The Weirdos Club." Following an event involving cryptid themes, she developed an avid interest in extraterrestrial phenomena and the occult magazine "Supernatural Encounters." Her name's etymology—"sun" (日) and "greens" (菜)—contrasts with Sayo's "night" (夜) kanji. In collaborative media like the Zombieland Saga Revenge crossover, her design was adapted to resemble Mizuno Ai, labeled "Legendary Student Council President." She also appeared in the shuffle band "Let's Enjoy an Exuberance Fun Band!" after winning a fan poll.