Description
Kokoro Tsurumaki leads the band Hello, Happy World as its vocalist while attending Hanasakigawa Girls' High School as a third-year. Her driving life mission, held since childhood, is spreading joy and making the entire world smile, fueling her passion for music and band activities.

Born into extraordinary wealth, her family possesses vast properties, including one of the area's largest residences, a private beach, a mountain, and a vacation home on the southern "Happy Happy Island." Their influence grants unique privileges like a personalized train pass displaying "Tsurumaki" instead of a balance and constant oversight by three bodyguards ("the suits") managing her energetic outbursts.

Kokoro radiates hyperactive, optimistic, and charismatic energy, effortlessly drawing people in with her bright, bubbly nature. Intense curiosity makes her easily amazed by new things, leading to open-minded acceptance of unconventional ideas—even developing a fondness for zombies after encountering horror media. Despite leadership qualities, her focus scatters constantly, requiring heavy reliance on bandmates, especially Misaki Okusawa, for task completion. Kokoro asserts she has never felt sadness and only learned the concept of stress from Marina at CiRCLE live house. Extreme wealth shielded her from common everyday norms understood by others.

She addresses everyone by first name without honorifics, reflecting an informal, egalitarian approach. Remarkable physical agility allows her to execute acrobatics like backflips even in restrictive furisode. Fan theories propose unrealized genius-level aptitude, citing instant mastery of skills like horseback riding, taiko drumming, and juggling.

Within Hello, Happy World, Kokoro's vision of global happiness directly shapes the band's endeavors. Her dynamic with bandmate Misaki (who performs inside the bear mascot Michelle) is central; Kokoro remains completely unaware of Misaki's dual role, steadfastly believing Michelle is a separate entity. This dynamic persists across all official media, including the spin-off *BanG Dream! Girls Band Party!☆PICO*, where her exaggerated cheerfulness fuels comedic situations—like initiating a beach volleyball game during a seaside episode or joining a mecha parody in *PICO FEVER!*. Her persistent drive involves the band in whimsical projects such as restoring an amusement park or performing on a drifting stage, showcasing unwavering commitment to spreading joy, though often necessitating others' intervention to manage ensuing chaos.

Collaborations like the *Ojamajo Doremi* crossover (styling her after Asuka Momoko) and the *Senki Zesshou Symphogear* event (influencing Akatsuki Kirika's card art) reinforce her thematic association with exuberance and creativity.