The third light novel of the Hibike! Euphonium series titled Hibike! Euphonium 3 Kitauji Koukou Suisougaku-bu, Saidai no Kiki (響け! ユーフォニアム3 北宇治高校吹奏楽部、最大の危機 Hibike! Euphonium 3 Kitauji Kōkō Suisōgaku-bu, Saidai no Kiki , lit. Sound! Euphonium 3 The Greatest Crisis of Kitauji High School's Concert Band) was released on April 4, 2015.
The main focus is on Mamiko's past and Kumiko and Mamiko's relationship as siblings. It also covers how Kumiko grows over the course of the year, but instead of focusing on her development as a musician, it mainly discusses the bonds she formed with Reina, Shuuichi, Hazuki, Sapphire, Asuka,
Natsuki, Mizore, Yuuko, Riko, Taki, and even her sister. It is these relationships that lead her to realize why she started playing music, and why she will to continue to play for as long as she can.
- By order of appearances:
- It is revealed that Reina only came to Kitauji High School because of Taki-sensei, and that she loved him in a romantic way.
- Shuuichi tries to grow closer to Kumiko and nearly confesses to her the night before their final concert. He also gives her a flower-shaped hairpin.
- Reina confesses to Taki-sensei that she loves him after the final concert when all the bands/mentors are being honored, but he takes that as a of respect and honor rather than a sign of romantic interest.
- Asuka mentions the hairpin on Kumiko after her graduation ceremony and asks if it’s from her “boyfriend”. Kumiko stumbles and eventually says "Yes." This is meant to show that Kumiko has mutual feelings for Shuiichi.
- Kumiko eventually confesses to Shuuichi that she loves him.
|Hibike! Euphonium novel series|
|Main series||Hibike! Euphonium Welcome to Kitauji High School's Musical Instrument Club • Hibike! Euphonium 2 The Hottest Summer of Kitauji High School's Musical Instrument Club • Hibike! Euphonium 3 The Greatest Crisis of Kitauji High School's Musical Instrument Club • Hibike! Euphonium 4 Kitauji Koukou Suisougaku-buno no Himitsu no Hanashi|
|Side stories||Hibike! Euphonium Series Rikka Koukou Marching Band he Youkoso Zenpen|