Masahiro Hashimoto returns to his alma mater, Kitauji High School, as percussion instructor. Hired by former college classmate Noboru Taki, he prepares the concert band for national competitions. Hashimoto himself played in Kitauji's "golden era" band under Taki's father, Tooru Taki, contributing to multiple national appearances.

He sports messy brown hair, green eyes, light stubble, and often wears large blue glasses. His wardrobe features colorful, flashy clothing like bright shirts or Hawaiian prints, accessorized with faux-leather watches, metal bracelets, and a yellow cord necklace. He stands noticeably shorter than Taki.

Energetic and fun-loving, Hashimoto connects with students using humor and nicknames such as "Hashimo-chan." Yet he leaps into rehearsals with professional rigor, demanding precision and expressive playing. He sometimes speaks without filtering his thoughts, inadvertently revealing personal details like Taki's private life. His teaching philosophy prioritizes musical enjoyment over competitive results, urging students to focus on expression, not awards.

A skilled percussionist with domestic and international performance experience, Hashimoto provides specialized coaching at Kitauji. He advises on ensemble balance, instrument arrangement, and stresses the crucial impact of a strong opening note.

Hashimoto and Noboru Taki forged a close friendship in college, often engaging in lighthearted mischief. After Taki's wife Chihiro (also their classmate) passed away, Taki distanced himself from friends, including Hashimoto. Years later, Taki's invitation to coach at Kitauji deeply moved Hashimoto, signaling Taki's emotional recovery and return to music. Their dynamic includes playful banter, like arguments over ramen broth preferences, reflecting mutual trust.

He shares collegial ties with woodwind instructor Satomi Niiyama, whom he and Taki treated like a younger sister at university. Hashimoto occasionally helps Niiyama understand Taki's perspectives. Though not a direct instructor to non-percussion students like Kumiko Oumae, he shows concern for their well-being, such as inquiring about Reina Kousaka's interactions with Taki to ensure appropriate boundaries.

Outside music, Hashimoto traveled internationally in his youth and maintains a hearty appetite, famously consuming large meals like three bowls of curry during band camps.