A male childcare guard-teacher working at Fujimiya Kindergarten within the Fujimiya Institution. He has warm hair colored like a blend of orange and red, styled in long, straight locks. With blue eyes bordering on purple and gentle, drooping lids, he exudes a calm and reassuring atmosphere. His uniform is specific to the childcare staff of Fujimiya Kindergarten, featuring a purple-based apron adorned with a wisteria patch symbolizing the Fujimiya Institution. As a guard-teacher, he also wears a purple guard uniform with a wisteria patch on the left chest and a purple guard cap, signifying his role as a specialist in both childcare and safety management. Ruki holds a kindergarten teaching license, childcare worker certification, and guard qualifications. He is responsible for the education, lifestyle support, and safety of the children at Fujimiya Kindergarten. He places great importance on protecting the future of each child so that their lives are not determined by their parents' criminal records or the prejudices of those around them. He himself experienced cold stares as a "child of a criminal" during his youth after his father lost his job due to a false accusation of molestation. Consequently, he sees his younger self in the children of the Fujimiya Institution, believing that "these children have done nothing wrong; it is the environment that hurts children that is at fault." While he has a mild and kind personality, he possesses a strong will when it comes to protecting the dignity and future of the children. His conviction is to look at the child themselves, not their parents' past, and support them so they can walk their own lives freely.

A boy living at Fujimiya Kindergarten. He is characterized by straight, long black hair and soft bangs. He has red eyes with thick, long lashes and usually wears a purple smock. His parents were leaders of a cult who were arrested for using their followers to commit theft and robbery for money. Seiyo was taken into protection at Fujimiya Kindergarten when he was two years old. He has a calm and gentle personality and enjoys playing with dolls. He is skilled at predicting feelings from others' expressions and actions, and is very observant of changes in his surroundings. He has a side that acts spoiled and invites trusted adults to play. Furthermore, he can stay close to children who are alone without forcing a distance, remaining mindful of their feelings.

A boy living at Fujimiya Kindergarten. He is the older twin brother of Saibi, with wavy light blue hair and green eyes, wearing a purple smock. His family was poor, and his parents became involved in smuggling work out of desperation. At age three, he and his younger brother Saibi were taken into protection at Fujimiya Kindergarten. He has a strong sense of responsibility and is always looking out for Saibi, who is a crybaby and prone to anxiety. He has a kind personality, holding Saibi's hand to reassure him and never taking his eyes off him. Having experienced the loss of his family in the past, he has a strong desire to "never lose precious family again," and his affection for Saibi is exceptionally deep. Despite his young age, he possesses a powerful drive to protect those he loves.

A boy living at Fujimiya Kindergarten. He is the younger twin brother of Saion, with wavy light blue hair and green eyes, wearing a purple smock. He treasures a dandelion crown made by his older brother Saion and always wears it on his head. His family was poor, and his parents became involved in smuggling work out of desperation. At age three, he was taken into protection at Fujimiya Kindergarten along with his brother Saion. He is filled with anxiety, believing the reason he was separated from his parents is because he was a "bad boy." He often clings to Saion in tears, pleading, "Don't leave me, I'll be a good boy." Though he is a sensitive crybaby, he has a heart so kind he won't even hurt a small insect, and he notices the pain and sadness of others more than anyone. He trusts Saion deeply as his precious family, and they are bound by a deep bond born from the fear of losing one another again.

A boy living at Fujimiya Kindergarten. Born into a fisherman's family in Okinawa, he speaks with a regional drawl. He is characterized by fluffy blonde hair with a small tail in the back, a snaggletooth, tanned skin, and gentle, drooping golden eyes. As a young child, he loved being carried on his father's shoulders and playing with a pinwheel his father bought him. He loves the smell of the sea and deeply respected his father as a fisherman. However, his father was arrested on suspicion of arson on a ship, and Senri learned of the incident. Senri believes his father is not the kind of person to do such a thing and told everyone it was a false accusation, but no one believed him, leading him to harbor a distrust of adults. He was taken into protection at Fujimiya Kindergarten at age three. His admiration and love for his father remain unchanged, and he vows to one day uncover the truth of who framed him. He possesses a strong sense of justice and conviction.

A male guard-teacher in charge of management at Fujimiya Kindergarten. He is characterized by hair with a white-to-blue gradient styled in a bob, black eyes with drooping lids, and long white lashes. He wears a purple guard uniform and cap, with the Fujimiya Institution's wisteria patch on his left chest. He is also a hacker responsible for anti-intruder measures, information management, and privacy protection systems, shielding the children from external dangers. He is a calm guardian who questions prejudice and irresponsible behavior, thinking, "It's wrong for these children to be made unhappy too."