Seiya Suzuki (鈴木 靖也 Suzuki Seiya) is a side character of Sound! Euphonium: The Movie - Our Promise: A Brand New Day film. He is a new first-year at Kitauji High School who joins the band as an alto saxophonist in Kumiko Oumae's second year.
Seiya is a very easygoing guy who often gets scolded by his fellow alto saxophone player Nanami Ootaki for talking with girls in the band.
- The name Seiya means "peaceful" (靖) (sei) and "to be, also" (也) (ya).
- Seiya's surname Suzuki means "bell" (鈴) (suzu) and "tree, wood" (木) (ki).
- Even though Seiya has the same surname as Mirei Suzuki and Satsuki Suzuki, they all have no familial relation with each other.
- Seiya is the troubled type that girls can't leave alone.
- Seiya is an experienced alto saxophone player and a graduate from Minami Junior High School.
|Kitauji High School Concert Band during Kumiko Oumae's second year|
|Note: Section leaders are shown in bold text|