Manaka is a fair-skinned, petite, and slender young girl noted for her delicate and innocent charm. She has long, straight auburn-brown hair that reaches past her shoulders, adorned with wing-like extensions behind her ears, an aquatic feature that can easily be mistaken for fins, symbolizing her origins from the sea. Her most prominent facial features are her large, expressive blue eyes, which are round and slightly wider than her forehead, giving her a youthful and emotive look.

Her sense of fashion leans toward traditionally feminine styles, often wearing dresses and outfits that emphasize her gentle and girlish personality.

Manaka is a sweet and bubbly middle school girl with an energetic spirit and an openly expressive nature. She has a fondness for cute things, particularly cat emojis and the color pink, which reflect her youthful and whimsical outlook. Initially, she comes across as indecisive and emotionally fragile, often trying to hold back her tears to avoid burdening others. This emotional restraint tends to frustrate Hikari Sakishima, whose teasing she oddly finds amusing, while it draws the quiet concern of her close friend Chisaki Hiradaira.

As the story progresses, Manaka undergoes notable emotional growth. Through her experiences, she begins to develop greater confidence and a deeper understanding of the emotions of those around her. Despite these changes, she never loses the kindness and warmth that define her core character.

Since childhood, Manaka was always closely surrounded by her friends Hikari Sakishima, Chisaki Hiradaira, and Kaname Isaki, who often looked out for her due to her timid and gentle nature. The group shared a strong bond growing up in Shioshishio, their sea village, and frequently spent time together.

One notable memory from her early years was when she and Chisaki got lost after venturing too far into the outer sea in search of coral. The two were eventually found and scolded by Hikari, who was deeply worried. Despite his sharp words, Manaka came to value the way her friends always supported and protected her, reinforcing her emotional reliance on them.

Hikari Sakishima: Hikari is one of Manaka’s closest childhood friends, alongside Chisaki and Kaname. Despite his short temper and frequent scolding of Manaka’s indecisiveness, the two share a deep emotional bond. Manaka once developed a short-lived crush on Tsumugu, which caused Hikari to distance his feelings, choosing instead to support what he believed were her romantic desires. Over time, Hikari comes to terms with his feelings and eventually confesses his love to her. However, Manaka, still uncertain about her emotions runs away in confusion. After the time skip, Hikari continues to show his devotion by searching for and eventually rescuing her. Though Manaka loses the ability to feel love upon awakening, it’s later revealed that she had always loved Hikari but concealed it for Chisaki’s sake. Their mutual feelings are finally acknowledged near the end of the series, where they watch the sea together, now certain of their bond.

Tsumugu Kihara: Early in the series, Manaka develops a crush on Tsumugu after he saves her. Her admiration grows as they spend more time together, but she later realizes her feelings stemmed more from gratitude and awe than true love. Manaka confides in Tsumugu, calling him the “sun”, someone warm yet distant and admits that her real feelings are for Hikari. Tsumugu keeps this confession secret until the appropriate time, helping Chisaki to move on from her own lingering emotions for Hikari.

Chisaki Hiradaira: Manaka and Chisaki have been best friends since childhood. Though they sometimes argue, their bond remains strong. A source of tension arises when both girls develop feelings for Hikari. Out of loyalty to Chisaki, Manaka suppresses her own feelings for him. Despite this, Chisaki continues to care deeply for Manaka and is always protective of her.

Kaname Isaki: Another member of their childhood group, Kaname shares a friendly and supportive relationship with Manaka. During moments of uncertainty, such as the approach of hibernation, Kaname is there to comfort and guide her.

Miuna Shiodome: Initially conflicted over her feelings for Hikari and Manaka’s return, Miuna struggles with jealousy and insecurity. However, as she gets to know Manaka, the two develop a caring relationship. Miuna ultimately plays a pivotal role in helping Manaka recover her lost feelings. It is revealed that Manaka unconsciously gave her ena to Miuna during the Ofunehiki to protect Hikari, further deepening their connection.

Akira Shiodome: After waking from hibernation, Manaka spends time with Akira and grows fond of him. When Akira, still a child, confesses his affection to her, she initially runs away, overwhelmed. However, she later thanks him sincerely. This moment helps Manaka rediscover what love means, marking a key step in her emotional recovery.