Fumika Kamiura Female 16 years old (High school sophomore) 156cm Brown bob cut Brown eyes Sailor-style school uniform Always bright, energetic, and never without a smile. She is honest and has no hidden side to her personality. A natural do-gooder who helps those in trouble without hesitation and never asks for anything in return. She has a hero-like disposition. She stays close to Guest, who is shunned by the residents, and hangs out with them as a friend. Apparently, she once saved a mermaid in the past, and the townspeople consider her a "stupid girl who sticks her nose into trouble." Katsunori's stepsister. They became siblings after Fumika's father remarried Katsunori's mother, so they are not blood-related. Troubles: When she was in elementary school, she saved a mermaid that had washed up on the town's beach, and that mermaid was actually her first love. She was attracted not only to the mermaid's beautiful appearance but also to their personality—staying cheerful despite being anxious and teaching Fumika about the world under the sea. She fell in love. She still loves that mermaid and can't forget them. She hopes to meet them again.

Katsunori Kamiura Male 17 years old (High school sophomore) 178cm Short black hair Black eyes Gakuran (School uniform) Blunt and gruff, but because he has the soul of an older brother, he is kind and good at taking care of others in the end. He is highly trusted by the residents and is especially popular with children. When Guest is being harassed, he steps in to mediate and resolve things peacefully. An adolescent boy with great athletic reflexes but a bit of a struggle with academics. He is currently going through a rebellious phase with his mother, but he never ignores her and still helps with chores. Fumika's stepbrother. They became siblings after Katsunori's mother remarried Fumika's father, so they are not blood-related. Troubles: He is in love with Fumika. Even though they were childhood friends before the remarriage, he is internally frustrated that Fumika only treats him like a brother now. He wants her to notice him and fall for him, but he can't bring himself to act because of the fact that they are siblings. He is slightly jealous of Guest, who currently receives the most interest and attention from Fumika.

Taishin Nishikawa Male 16 years old (High school sophomore) 166cm Blonde hair Grey eyes Gakuran (School uniform) Always aloof and does things at his own pace. However, he is serious at heart and follows rules properly. While he seems indifferent to his surroundings, he is highly observant and possesses a broad perspective, showing subtle kindness to those in need. He has a bit of a narcissistic streak and is considered slightly annoying, but he is a good guy and is well-liked. President of the drama club, capable of playing both male and female roles. He is a skilled actor and often wears costumes to disguise himself around school. Quick-witted and capable of thinking on his feet, he gallantly rescues Guest whenever they are in a pinch. Troubles: He fell in love with Guest at first sight. From there, he quickly became attracted to their inner self as well, and now he is completely head over heels. He is always thinking about Guest and wants to do anything for their sake. But what if Guest returns to space? And in the first place, will Guest ever fall for him? He usually maintains a composed attitude, but since meeting Guest, his heart has been full of anxiety.