Kujima is a mysterious, bipedal creature with a bird-like appearance that stands out as neither entirely human nor animal. His tall, slender frame, long beak-like proboscis, and gangly, tube-shaped build give him a surreal presence. He was raised in Russia by an elderly man before arriving in Japan, which explains his fluent yet noticeably accented Japanese, marked by rolled Rs and off-kilter intonation. Kujima is talkative, curious, and driven by a straightforward desire for food and shelter, especially a fondness for Japanese cooking. Hungry and resourceful, he is first encountered by middle school student Arata Kōda while trying to fish a coin out from under a vending machine one autumn day. Arata brings him home, and despite initial resistance from the household, Kujima ends up staying as a temporary freeloader through the winter.

At the Kōda residence, tension runs high because Arata’s older brother Suguru has retreated into his room after failing college entrance exams, disrupting family meals and creating a strained atmosphere. Kujima quickly senses the underlying loneliness and emotional disconnection, particularly Arata’s yearning for his brother’s company. Though his presence is at first unsettling and his behavior odd, he shows genuine gratitude to the family and quietly takes it upon himself to ease the household’s stress. He interprets unspoken needs, nudges relationships, and devises small schemes to encourage Suguru to rejoin family dinners, effectively becoming the catalyst that helps the family reconnect.

Kujima’s personality blends cheerful eccentricity, blunt honesty, and unexpected perceptiveness. He often expresses himself in exaggerated, comedic ways, but beneath the oddness lies a sincere wish to repay kindness and restore warmth to the home. His motivations evolve from simple survival—having a place to stay and enough to eat—into a deeper commitment to the well-being of the people who took him in. Although he can come across as grating or overwhelming, his actions consistently aim to heal the fractures in the Kōda family.

The key relationship is with Arata, who first offers him food and a roof, and whom Kujima comes to see as a trusted friend. Through Arata, he connects with Suguru; though the older brother is initially hostile, Kujima’s persistent, if peculiar, interventions gradually draw Suguru out of his isolation. He also interacts with the parents, Miyoshi and Masaomi Kōda, who move from bewilderment to a quiet acceptance of his presence. Another creature named Maxim appears in supporting roles, hinting at a world beyond the ordinary, but Kujima’s primary anchor remains the human family.

Throughout the story, Kujima’s development shows a shift from a hungry stranger into a beloved, albeit bizarre, household member. He learns to read human emotions more finely and channels his gratitude into active caregiving, even if his methods are unconventional. His notable abilities are his human-like speech, his knack for social observation, and the subtle, almost supernatural influence his presence exerts—his singing or warbling is implied to have unusual effects, though the exact nature remains gentle and atmospheric rather than explosive. He does not possess combat skills or magical powers; instead, his impact comes through conversation, companionship, and an uncanny talent for disarming tension and drawing people together. In the end, Kujima is defined by his role as an unexpected breath of fresh air that transforms a stressed household into a more open and affectionate family.