Sound! Euphonium: The Movie - Our Promise: A Brand New Day

After swearing off music due to an incident at the middle school regional concert band competition, euphonist Kumiko Oumae enters high school hoping for a fresh start. As fate would have it, she ends up being surrounded by people with an interest in the high school brass band. Kumiko finds the motivation she needs to make music once more with the help of her bandmates, some of whom are new like novice tubist Hazuki Katou; veteran contrabassist Sapphire Kawashima; and band vice president and fellow euphonist Asuka Tanaka. Others are old friends, like Kumiko's childhood friend and hornist-turned-trombonist Shuuichi Tsukamoto, and trumpeter and bandmate from middle school, Reina Kousaka. However, in the band itself, chaos reigns supreme. Despite their intention to qualify for the national band competition, as they currently are, just competing in the local festival will be a challenge—unless the new band advisor Noboru Taki does something about it.

The third season of Hibike! Euphonium . Kumiko's third year finally begins! With the concert band at Kitauji High School over 90 members, Kumiko is now the president and does her best with her final high school club activities to try to win her long-desired gold at nationals.

Spring in the first year of high school. Kumiko, a member of the brass band in junior high school, visits the high school brass band club with classmates Hazuki and Sapphire. There, she comes across Reina, her former classmate from junior high. Hazuki and Sapphire decide to join the club, but Kumiko can’t make up her mind. She recollects her experience with Reina at a competition in junior high school.

With another tournament fast approaching, Kumiko's band is doubling down on practice and discipline, leaving little time for sleep or other recreational activities. The redoubled practice schedule brings Kumiko and Reina closer together, but elsewhere in the band, it seems like drama threatens to tear the group's unity apart. The ghost of the prior year's mass band exodus still haunts many of Kumiko's classmates, and with former band member Nozomi Kasaki now asking to return, it seems like the grudges of the past will soon be impossible to ignore. Note: The first episode aired with a runtime of ~48 minutes as opposed to the standard 24 minute long episode.