Koharu dreams about travelling around the world. She desires to make new experiences and wants to learn how to speak in front of strangers. Koharu hopes to overcome her shyness one day.
Koharu is a first year middle school student, who attends Southern Lights Academy and attends language classes. Her most favorite classes are English and French. Koharu's biggest dream is to travel the world and make new experiences on her journey. Due to being rather shy, Koharu desires to learn how to speak in front of strangers and how to rise her voice. She wants others to know about her, to hear her and to understand her. Right now, the only ones she is able to talk normally with are her family and her best friend Chiasa. If Koharu has to talk with others, she speaks with a quiet voice, or even hides behind Chiasa. Koharu truly dislikes her shyness but apparently can't fight it.
During the series, Koharu learns to speak up and becomes a bit more confident about her own opinion and her own voice. She becomes more confident with the words she chooses. Koharu eventually starts to mix her sentences with English or French words, and even gets brave enough to make jokes. Over the time, she shows that she might be shy at first, but as soon as she warms up to someone, she becomes outgoing and happy-go-lucky.
When being around her friends, Koharu tends to say "100 % exciting!" (「１００％ワクワク！」 '100-Pāsento wakuwaku!'?) a lot.
Koharu has brown colored hair, that she usually keeps opened. She has brown eyes. In civilian, Koharu usually wears a white colored long sleeved top on which "100%", Koharu's favorite words, is written in purple color. Over the top, she wears a khaki colored sleeveless vest which reaches down to her hips. She wears black jeans shorts and white boots.
- Tenaka Chiasa: Chiasa is Koharu's very best friend since childhood, who is the only person she can talk normally with. Chiasa finds Koharu's shyness rather cute, even though she doesn't understand how she could be so calm and why she hides behind her all the time.
- Asahi Honoka: Asahi Honoka is Koharu's mother. Honoka used to work as a flight attendant. However, due to an injury, she had to quit her job. Today, she is completely dedicated to her family. She enjoys the time she can spend with her Koharu and Kyou.
- Asahi Tsukasa: Asahi Tsukasa is Koharu and Kyou's father, who lives together with his family in Hisakata Town. Tsukasa is a strict, yet nice and very gentle person, who wants his children to be able to become what their dream to become in the future.
- Asahi Kyou: Asahi Kyou is Koharu's older brother. He's older by two years and attends the same school as his sister. Much like his sister, Kyou is very kind and tender towards anyone. He may be a little stubborn can be a very good friend.
Asahi (朝日?) - Asahi comes from Asa (朝?) meaning "morning", "dawning" or "brightening", combined with Hi (日?) meaning "sun" or "day". Asahi can be translated "morning sun" or "brightening sun". Asahi could also mean "brightening of the morning sun".
Koharu's character songs are provided by Kajiwara Ai, her voice actress. While Koharu has her solo songs, most songs produced by Kajiwara Ai are either duets or group songs with the other voice acresses.
- １００％！ is Koharu's first solo song, which is sung by Kajiwara Ai. It is featured in the first vocal album.
- Koharu's favorite words are "100%".
- Koharu's birthday falls on March 3rd and star sign is Pisces.