Sapphire Kawashima (川島 緑輝 Kawashima Safaia ) is one of the main characters of the Hibike! Euphonium series. She is a classmate of Kumiko's and Hazuki's, and she is a contrabass player in the Kitauji Concert Band.
Sapphire also dislikes her real name, preferring to be addressed as Midori (緑).
Sapphire is a young teenage girl of below-average height and weight. She has a petite build, and she is the shortest of the main characters, if not the whole band. Sapphire has messy and wavy chin-length blond hair. One of her defining physical traits is a strand of her hair sticking up from the back of her head. She has greenish-lime eyes and somewhat thick eyebrows, and wears a turquoise hair bow with light green polka dots.
Sapphire is usually seen with a normal Kitauji High School uniform for first-year female students.
Sapphire has a positive personality, and she always puts her friends before herself. She worries quite a lot but she is naturally cheerful and happy. Sapphire is a girl who has soft hair and a delicate constitution. She is often timid and quiet due to her lack of self-confidence, and she is also very embarrassed by her own name. However, she is very kind, caring and polite, and also very supportive of her friends. She is also passionate about music, treasuring her string bass and even giving a name to it, "George". She often continues to play it even though she may have hurt her fingers; which happens quite often.
Sapphire is from a rich family and studied in an elite junior high school for young ladies, where she learned to play the contrabass. She joined the concert band to continue to play music.
On her first day in Kitauji High School, when the teacher was calling up all the students name, the teacher got Sapphire's name wrong, making her embarrassed and instantly blush. After that, the teacher said that she won't make the same mistake again. Afterwards, she later befriended Kumiko Oumae and Hazuki Katou, and Hazuki told her to call them by their first names.
Sapphire gets along with Kumiko very well and they are close friends. Kumiko and Hazuki are Sapphire's first friends upon entering Kitauji. Sapphire and Kumiko support and care for each other, and they can freely talk about various topics and they trust each other.
Sapphire and Hazuki are also great and close friends and they care and trust for each other a lot. Hazuki could openly tell Sapphire and Kumiko about her crush on Shuuichi. The two support each other and Hazuki can open up to Sapphire, like when she cried in front of Sapphire when she got rejected, and Sapphire comforted her. They can also talk about various topics with each other and Hazuki also seems to quite fond of Sapphire's younger sister. They are on good terms and share a close bond.
- Sapphire loves pets, especially reptiles and iguanas (she has an iguana named Macaron).
- She has a little sister named Kohaku.
- Her name, Sapphire (緑輝 Safaia ), means "green brilliancy".
- After school, she often goes to the prize dispensor where she plays for musical instrument charms. It appears that she is looking for a 'Tuba-kun' charm, and is shown disappointed when receiving Sax-kun and Horn-chan.
- She participates in Color Guard in the marching band, due to the size of her instrument.
- Kumiko, Hazuki, and Midori are all in Year 1, Class 3 in the book series.
- Midori's homeroom teacher is Michie Matsumoto.
- Midori originally wanted to play the Flute before the Contrabrass.