Sapphire "Midori" Kawashima (川島 "緑" 緑輝 Kawashima "Midori" 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 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, preferring to be addressed as Midori (緑). However, she is very kind, caring and polite, and also very supportive of her friends. She is also passionate about music, treasuring her double 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 attended Seijoh Junior High, an elite all-girls school, 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 befriended Kumiko Oumae and Hazuki Katou, and Hazuki told her to call them by their first names.
- According to the official Sound! Euphonium novel website,
- Her favorite colors are pink and pastel colors.
- Her hobbies are making sweets and collecting stuffed toy animals.
- Her special skills are cooking and sewing.
- She has a pet iguana named Macaroon.
- She hates computers because she doesn't know how to operate one.
- She has a little sister named Kohaku.
- Her name, Sapphire (緑輝 Safaia), means "green brilliancy".
- After school, she often goes to the prize dispenser 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 contrabass.
- She wants to go to design school. 
- She has a giant Japanese salamander plush she purchased at the Kyoto Aquarium named Kaiser.