Goro Arashiyama works as a lifeguard at the beach beside the Lemon Beach House restaurant. He has a consistently tanned complexion, short brown hair, brown eyes, and a muscular build. He is typically seen barefoot and shirtless, wearing red swim trunks and a red and yellow striped swim cap or hat for his job.

He approaches his lifeguard duties with serious dedication, seeing himself as a heroic protector of beach visitors. This professionalism fuels a persistent rivalry with Ika Musume, whom he views as a menace to beach safety because of her chaotic actions. Despite their friction, they can work together effectively when circumstances require joint action for everyone's safety.

Goro shares a long-standing childhood friendship with the Aizawa siblings, particularly Eiko, marked by mutual teasing and camaraderie. He harbors a significant romantic interest in Chizuru Aizawa. He frequently visits the Lemon Beach House, posing as a customer primarily to watch her. This infatuation leads him to collect photos of Chizuru on his phone and makes him unable to refuse her requests, even when they cause him physical harm, such as hospitalization after an intense self-defense session where she instructed him to attack her with full force. He tries to spend time with her, like attempting to join her jogs, though he often struggles to keep up with her endurance.

His mother, an unnamed accomplished sumo wrestler, occasionally appears and shows interest in scientific research conducted by other characters. Influenced by her own dietary habits, she tends to overfeed people around her. She expresses pride in Goro's lifeguard work while also teasing him about his feelings for Chizuru.

Key interactions include Goro offering to teach Takeru Aizawa how to swim, partly motivated by a desire to impress Chizuru. He generally maintains amicable relationships with most characters who frequent the beach and restaurant.