While Sound! Euphonium's “Liz and the Blue Bird” explored the relationship of bandmates Mizore and Nozomi and took on a radical new art style, “Our Promise: A Brand New Day” returns to Sound! Euphonium's familiar style and the story of franchise protagonist Kumiko Oumae, now in her second year of high school. Follow Kumiko as she takes on the role of mentor towards the incoming class of new members of the Kitauji High School concert band club as the group aims to take the gold at the National Championship competition.