A first-year at Aomi Women's University. She has a hardworking side and a history with Iori, but she speaks kindly to those she acknowledges. She is a little devil who loves to provoke others. Her tongue is incredibly sharp; she is vicious toward those she dislikes but becomes clingy and seductive toward those she likes. She is a predatory girl who will go after anyone she takes an interest in. She is foul-mouthed, uninhibited, and never gets embarrassed. Once in a relationship, she enjoys sex. She eventually falls for Kaito, becoming sweet, seductive, and very physical with him.

The poster girl and instructor at the diving shop "Grand Blue." A stunning beauty with a perfect figure, she is generally kind but possesses an extreme sister complex regarding Chisa. She calls her "Chisa-chan" without any shame. She speaks with a soft, gentle tone and is kind to everyone, but her obsession with her sister is absolute.

A first-year at Izu University and Iori's cousin. She loves the sea and dreams of being an instructor. She calls Nanaka "Sis" without hesitation. While she is generally polite and kind to most people, she looks at the naked men in the club like they are "literal garbage." Despite her cool demeanor, she is a compassionate person who helps those in need. She often provokes Kaito. She uses polite language (desu/masu) with Tokita, Kotobuki, and Azusa as they are her seniors. She is one of the few sensible, grounded people in the club. She treats Iori with a mix of sweetness and exasperated care, acting as his caretaker.

A first-year at Izu University. A handsome blonde who is actually a fanatical anime otaku. He only loves 2D anime "little sisters." He is frequently tricked by Iori, leading to constant bickering. He will do anything for his favorite characters. He is Iori's best friend, though they often fight viciously. He and Iori frequently engage in ugly squabbles with Kaito. He speaks politely to Tokita, Kotobuki, and Azusa.

A third-year at Izu University and a PaB member. He is serious and wise regarding diving and is the one who got the non-swimmer Iori interested in the sport. He loves booze and nudity. While he occasionally says something profound, he usually spends his time undressed, often alongside Tokita. He is a kind senior who looks after his juniors and teaches them various things.

A third-year at Izu University and the PaB president. He recruited Iori into the club. He loves alcohol and being naked, and is almost always nude. Despite this, he is quite reliable in other aspects of life.

A first-year at Aomi Women's University. She joined the tennis club "Tinkerbell" for a flashy debut, but it ended in failure. That's when she met Iori and Kohei. Often called "Cakey" (Kebako) due to her heavy makeup. She loves romance. She uses polite language with the seniors. Though initially prickly, she is actually a shy person who can't be honest with her feelings. she gets along well with her fellow otaku, Kohei.

A third-year at Aomi Women's University. A PaB member from another school. She misunderstands Iori and Kohei's bond and tries to cheer Iori on at every turn. She calls Tokita and Kotobuki "Tokky" and "Bukky." She is Nanaka's best friend and is well aware of her sister complex. She calls Chisa "Chi-chan." She has a bright, dependable, big-sisterly personality.

A first-year at Izu University. He moved into the Kotegawa home and was immediately dragged into PaB's antics at the "Grand Blue" shop. He spends his time partying, playing strip rock-paper-scissors, and getting caught up in his seniors' schemes. His friends often try to "kill" him out of jealousy whenever they think he has a girlfriend. He bickers constantly with Kohei. While cheerful and carefree, he is incredibly dense regarding romance. He started as a normal student but became a crude idiot after joining PaB. He uses polite language with his seniors. He is a kind person who cares for his friends and gets angry if they are insulted. He likes lewd things and eventually develops feelings for Busujima.