Kaname Isaki has soft, beige-colored hair that falls around his face in gentle layers, giving him a calm and composed look. Like all residents of Shioshishio, his eyes are a striking shade of blue, reflecting his origin from the sea.

He is typically seen wearing his school uniform, both before and after the time skip. Kaname is considered to be quite handsome, as noted by Sayu Hisanuma and several of Miuna Shiodome’s classmates, who occasionally comment on his refined appearance.

Kaname Isaki is calm and easygoing, often choosing to go with the flow rather than stir up conflict. He tends to observe situations with quiet composure and avoids getting swept up in emotional outbursts. Although he’s supportive of his friends, he sometimes expresses mild frustration when Hikari becomes overly headstrong or impulsive. Kaname also keeps his deeper thoughts and emotions to himself, rarely revealing what he truly feels beneath his collected exterior.

Kaname Isaki grew up in the sea village of Shioshishio alongside his childhood friends Hikari Sakishima, Manaka Mukaido, and Chisaki Hiradaira. Among the four, Kaname is often seen as the most composed and observant, often acting as the calm mediator in tense situations.

As the story begins, Kaname transfers with the others to a surface school after their underwater school closes. He quickly becomes aware of the complex emotions among his friends, especially Hikari’s feelings for Manaka and Chisaki’s hidden affection for Hikari. Despite harboring feelings for Chisaki himself, Kaname quietly supports his friends and hides his own emotions.

During the Ofunehiki ceremony, Kaname, along with Hikari and Manaka, falls into a deep hibernation under the sea, while Chisaki is the only one who remains awake and lives on the surface.

After the five-year time skip, Kaname is the last of the three to awaken. Unlike Hikari and Manaka, who reappear near the shore, Kaname emerges near the bottom of the sea and is later discovered by Sayu Tsugiyoshi. His return is quiet and somewhat distant, as he finds himself adjusting to the changes that occurred during his absence, especially Chisaki’s growing closeness with Tsumugu.

Despite the emotional strain, Kaname continues to support his friends, even confronting his own feelings and accepting that Chisaki has moved on. Eventually, Kaname begins to open up more emotionally, particularly toward Sayu, who confesses her love for him near the end of the series.

Sayu Hisanuma
Sayu has held feelings for Kaname since childhood, especially after he helped her open up and form friendships with others, including Hikari Sakishima. Even after growing older, her affection for him remained unchanged. Though she tried to move on, Kaname remained the central figure in her heart. Motivated by her feelings, she confides in Miuna Shiodome that she intends to confess to him.

After overhearing a conversation between Tsumugu and Chisaki, Kaname walks away quietly, only for Sayu to chase after him. She chastises him for hiding his feelings, particularly his unrequited love for Chisaki. Kaname responds that revealing them wouldn’t have changed anything, as Chisaki’s feelings were always directed toward Tsumugu. Sayu then confesses her love, telling Kaname that she had always been waiting for him, which deeply moves him. Touched by her sincerity and devotion, Kaname breaks down in tears, having believed that no one had been waiting for his return after the Ofunehiki. He begins to see Sayu in a new light, now that they are the same age, and decides to give her a chance.

During the second Ofunehiki, Kaname chooses to save Sayu from falling overboard, symbolizing that he has decided to let go of his feelings for Chisaki and move forward with Sayu. In the final episode, the two are seen smiling warmly at each other, implying that their relationship has blossomed and will likely continue to grow.

Chisaki Hiradaira
Kaname has been a quiet source of support for Chisaki throughout their childhood, often being the one to cheer her up during difficult moments. As the hibernation approached, Kaname chose to confess his feelings to her, doing so outside her home and unintentionally in front of her parents. The confession left Chisaki unsure of how to respond, and their dynamic became somewhat strained afterward.

Following the confession, Chisaki briefly considered confessing her own feelings to Hikari, but Kaname intervened by prompting Hikari to admit his love for Manaka instead. Though this created temporary tension between Kaname and Chisaki, she later came to understand his actions. Ultimately, Chisaki did not reciprocate Kaname’s feelings, and their relationship settled into a more platonic one as she moved on with Tsumugu, while Kaname began to open his heart to Sayu.