Kokona Tagawa (田川 ここな Tagawa Kokona) is a student from class 3-B and Megu Kataoka's former classmate who essentially blackmails Megu to help her study after Kokona nearly drowned from failing to learn how to swim.
Kokona has wavy dark-colored hair that is tied in pgtails by pearl hair ties and dark-colored eyes with long lashes and a round face.
Kokona is a self-centered and selfish girl, due to her neglecting Megu's need to study for her own grades and making her feel guilty for Kokona's incident. She thought that after just a bit of swimming practise she would be good enough to swim in the sea. The title of her own pick-up box is "Doesn't the world exist solely for me?!", hinting at her egoism. She loves the spotlight.
Kokona and Megu meet after Megu was practising swimming so that she could help Kokona study for the upcoming exams. Nagisa, Kayano and Koro-sensei shortly after find out that Kokona is blackmailing her. They question Megu and she reveals that she has taught Kokona how to swim, but she still has been too inexperienced to swim in the sea, so she almost drowned in the sea after trying to impress her crush. Afterwards Kokona used the incident as blackmail material.
To stop that, the four of them organise a plan to help Kokona overcome her fear of water. In her sleep, they bring her to the lake at the mountain and disguise themselves. They trick Kokona into thinking that she is dreaming while helping her trying to swim against the flow.
The next day, Kokona has swimming class and gets told that she improved drastically. Megu notices that and says how it seems like Kokona doesn't need her help anymore.
Megu and Kokona used to be friends because they were in the same class in middle school. Megu taught her how to swim, and even though Megu wanted her to practise more, Kokona went swimming in the sea which resulted in her almost drowning. Afterwards she guilt-tripped Megu into helping her study at all times. They stopped studying together after Megu saw that Kokona improved her swimming.
- Kokona's surname Tagawa means "field, rice paddy" (田) (ta) and "river, stream" (川) (kawa/gawa).
- Kokona was omitted in the anime.
- Kokona last appearance is in Chapter 118, visiting the restaurant of Class E together with Kaho Tsuchiya.
- Kokona had a traumatic fear of water, swimming and the sea.
- After overcoming her fear, she came to love swimming and swims three times a week.