Chisa Kotegawa (古手川 千紗 Kotegawa Chisa? ) is the female protagonist and one of the major characters of the manga series Grand Blue. She is a first year Mechanical Engineering student at Izu University.
Chisa is of average height and build with short brown hair, brown eyes and she has been described as cute by other characters where Iori Kitahara has made several comments about her body, particularly her big butt, in which he calls "spectacular".
She has the second smallest bust among the female characters and although she is conscious of it, she isn't as concerned about her chest size as much as Aina Yoshiwara.
Chisa is initially seen as a level-headed and serious girl who takes her studies seriously. She is rarely seen taking part in Peek-a- Boo's drunken antics, usually sitting off and observing instead. Though this makes her seem cold, she actually avoids such antics because she is extremely weak to alcohol (this may be the normal reaction, as Peek-a-Boo's alcoholic beverages usually have above 90% alcoholic content).
She loves diving and is usually the most eager to do any diving related activity. She abhorred the example set by her fellow club members, and was quite hostile when her friends attempt to involve her in their antics. She is incredibly stubborn; once having set her mind on something being almost impossible to convince otherwise.
Despite being considered beautiful and getting hit on constantly in her university, Chisa is disinterested in romance. She aspires to be a diving instructor.
- Toshio Kotegawa: Chisa's father. Not much is known about their relationship as they rarely interact with each other.
- Sayaka Kotegawa: Chisa's mother whom she has a strained relationship, this is due to a misunderstanding resulted from Sayaka's inability to show her true feelings. When Chisa arrives to Palau, she helps out around her mother's diving shop, and due to Sayaka's reluctance and disapproval of Chisa's aspirations to become diving instructor, combined with the fact that Chisa thought Sayaka was ignoring her when she went to cement and persuade her to not disapprove of the idea, eventually lead to Chisa storming off. However it is clarified, when Iori comes back from Palau a day after Chisa, that Sayaka was deaf in the left ear, hence Chisa misunderstanding that Sayaka was ignoring her. Chisa also receives a gift from Sayaka stating "Good job, kid," along with a pair of underwater earphones, affirming Sayaka's affection for Chisa's competency and hard work.
- Nanaka Kotegawa: Chisa's older sister whom she has a close relationship with and she seemingly looks up to her, although she is oblivious to the fact that Nanaka is a sis-con.
- Iori Kitahara: Chisa's cousin who she initially dislikes for his tendency of being roped in most of PAB's shenanigans, particularly being drunk and naked. Despite this, they are capable of working really well together and she can sometime show a level of compassion towards him especially when it comes to his interest in diving. It is later revealed that they are not related by blood since Iori's father is adopted by her maternal grandparent. During a misunderstanding where she believed Iori to have genuine romantic inclinations for her, she grew afraid and distant as she feared their relationship would change. During Kouhei's hypnotization, Iori unknowingly involves Chisa, causing Chisa to direct all her love of the ocean towards second most important thing in her life, of whom is Iori Kitahara. Despite this and many other events pushing the two closer, it is unclear if Chisa has feelings for Iori.
- Shiori Kitahara: Chisa's younger cousin. Not much is known about their relationship other than they are quite close. Like Iori, they are not related by blood despite being cousins.
- Azusa Hamaoka: Azusa, on more than one occasion, has commented on Chisa, calling her cute.
- Aina Yoshiwara: Chisa is good friend with Aina, and the two hit it off quite well. However, she has yet to realize Aina's envy towards her.
- The name Chisa means "thousand" (千) (chi) and "thread, silk" (紗) (sa), which literally means "A Thousand Soft Silk" altogether.
- Chisa's surname Kotegawa means "old hand, disused article, retired official, ex-soldier" (古手) (kote) and "river, stream" (川) (kawa/gawa).
- Chisa is one of three female students in her class who is idolized by her male classmates due to the lack of females in her major.
- Chisa has a preference for sweets..
- Grand Blue Volume 12 Chapter 46, Page 14