Motomu Tsukinaga is a first-year double bass player in Kitauji High School's concert band, joining alongside fellow newcomers Kanade Hisaishi, Mirei Suzuki, and Satsuki Suzuki. He possesses fair skin, short gray-black hair parted on the right, and distinctive aqua-teal eyes.

Despite an adorable appearance, Motomu exhibits a crabby, irritable personality. He intensely dislikes being called cute or referred to by his surname. His background as the grandson of a famous conductor creates internal pressure, contributing to his detached demeanor and reluctance to discuss personal matters, making him seem distant.

Within the band, Motomu struggles to connect with senior members, widening the emotional gap between new and existing students. He harbors a specific dislike for Kanade Hisaishi. His integration progresses gradually, spurred by a developing interest in fellow band member Sapphire Kawashima; their mutual attraction is subtly conveyed through interactions.

Motomu's interests include astronomy, stargazing (with a preference for winter stars), and building dioramas. He enjoys recycling marks and admires the Tower of the Sun. His favorite colors are greenish-brown and thin yellowish-green. A notable personal quirk is his distinctive talent for dazing off for extended periods.

His character development involves overcoming initial resistance to band camaraderie, influenced by his grandfather's legacy. His journey reflects themes of reconciling personal identity with external expectations as he contributes to the ensemble's challenges in pursuing national competition success.