Thoroughly serious with a brother-first attitude and a hidden dependency. An ordinary, serious, kind young man. A public servant working in the General Welfare Section of the city hall, seen by those around him as an extremely kind and serious young man. He never neglects to consider others.
Loves routine, lives like a calm sea. Because his younger brother Mito can only live within a fixed routine, Koto himself also keeps his own life and emotions constant, hoping for a calm, everyday life where nothing happens. At first glance, he is a self-sacrificing and kind older brother, having given up his own dreams and further education for the sake of his brother.
However, he also has an essential weakness and clumsiness: a deep psychological dependence on his brother, as he can only find his own reason for existence through supporting him.

A young man with Autism Spectrum Disorder.
He has a distinct personality and behavioral patterns based on those traits. He places the utmost importance on strong routines and a regular, orderly life. He strongly dislikes irregularities such as unexpected events or anything different from the norm. He is pure and straightforward, unable to tell lies, expresses his emotions honestly, and says exactly what he thinks. He has no ulterior motives or malice, always possessing a sincere and pure heart towards his own world.
He possesses overwhelming artistic sense and outstanding talent in the fields of perception and art. He has an excellent memory for accurately capturing things he has seen once and a great sense of color. He utilizes this ability as an artist belonging to and working for a small design company called "Planet Home."
He has a unique way of speaking, talking a bit quickly and rattling on, as if trying to convey information accurately.

The son of Ai Tachibana. He had been living in hiding with his mother, who could no longer endure the moral harassment and domestic violence from his father. After his mother was involved in an incident, he was entrusted to the Komori brothers and began to act together with them, going by the name Lion.
His personality has innocent and tough aspects. Even when suddenly thrown into a world of unfamiliar adults, he has a sensible side, sensitively sensing the situation as a child and showing his own will and bravado. He also has a childish and affectionate nature, being innocent and clingy for his age. Through his life with the Komori brothers, he gradually opens his heart and regains his human warmth.

Tora-jii's personality is extremely gentle and caring. He is a kind, loving character who quietly continues to support the Komori brothers, who lost their parents.
He is generous and包容力がある (has great capacity for acceptance). He lends a hand when the brothers are in trouble, and when they find themselves in a pinch partway through the story, he generously lends them his own villa. He is a very open-hearted and reliable person.

Koto's half-sister.
She was abandoned by her biological mother, came to live with the Komori family at age 15, but ran away from home at age 18. Afterwards, she married Shogo Tachibana, who runs a construction company.
Past and Personality: Originally a loving and gentle person, she couldn't endure the severe domestic violence from her husband, Shogo, and decided to flee to protect Lion. She went into hiding in order to entrust her child to a safe place.

Director of the construction company "Tachibana Urban Development" in Yamanashi Prefecture (entered the Tachibana family as an adopted son).
He grew up in a facility from childhood and has borne the position and heavy pressure of inheriting the family. On the surface, he appears quiet and expressionless, making it hard to tell what he is thinking, but within the home, he had a twisted side that subjected Ai and Shuto to controlling, oppressive domestic violence (abuse).