Age: 18 Residence: Grand Blue, a diving shop run by his uncle on the Izu Peninsula Personality: Bright, mischievous, loyal, and takes good care of his friends Relationships: Chisa Kotegawa's cousin, best friends with Kohei Imamura Gender: Male Affiliation: Izu University, Department of Mechanical Engineering / Diving Club (PaB)

Age: 18 Affiliation: Izu University / Diving Club (PaB) Residence: Izu area (University dormitory) Personality: Strong otaku tendencies, eccentric but loyal and cares for his friends Relationships: Iori Kitahara's best friend, a duo that constantly gets into trouble together Gender: Male

Age: 18 Affiliation: Izu University / Diving Club (PaB) Residence: Izu area, Diving Shop (Grand Blue) Personality: Calm and composed, diligent, and truly loves diving (but becomes terrifying when angered) Relationships: Iori Kitahara's cousin, though they are not blood-related; shows interest in Iori Gender: Female

Age: Around 20 Affiliation: Employee at Diving Shop (Grand Blue) Residence: Izu area (Grand Blue) Personality: Kind and gentle, but displays a strong obsession(?) toward Iori Relationships: Chisa Kotegawa's older sister; likes Iori Kitahara (not blood-related) Gender: Female

Age: 40s Affiliation: Owner of Diving Shop "Grand Blue" Residence: Izu area (Grand Blue) Personality: Jovial and mischievous, loves diving and drinking Relationships: Father of Chisa and Nanaka Kotegawa, uncle to Iori Kitahara Gender: Male

Age: Early 20s (University student) Affiliation: Izu University / Diving Club (PaB) Residence: Izu area Personality: Boisterous and optimistic, loves alcohol and diving, takes good care of his juniors Relationships: Senior to Iori and Kohei, alongside Shinji Tokita Gender: Male

Age: Early 20s (University student) Affiliation: Izu University / Diving Club (PaB) Residence: Izu area Personality: Blunt but jovial, very mischievous and enjoys drinking Relationships: Senior to Iori and Kohei, same year as Ryujiro Kotobuki Gender: Male

Operator: Toshio Kotegawa Business: Diving Shop (Scuba diving equipment sales and training) Key Figures: Chisa Kotegawa, Nanaka Kotegawa, Iori Kitahara Features: A seaside diving shop where Iori stays as he begins his college life Atmosphere: Energetic and noisy, feels like a hideout where friends gather Activities: Drinking parties, pranks, games, diving practice, playing in the ocean Characteristics: A place where the members' comedy and social activities stand out more than actual diving Vibe: Feels like the "free summer vacation of college students near the sea" Main Activities: Diving, parties, traveling, betting, pranking, hanging out together