Kanata Saionji, also known as Cody Kiyama in some versions of the anime, is a central figure in the story as the male protagonist who finds his life dramatically changed by an unexpected living situation. He is a high school student living at a temple, which serves as his family home. His ordinary life takes a turn when his father, a priest, abruptly announces a year-long trip to India for spiritual enlightenment, leaving Kanata alone in the large temple. The situation becomes even more complicated when a girl named Miyu Kozuki arrives, sent to live at the temple by her own mother who is working abroad. This forces Kanata and Miyu to live together under the same roof, a secret they must carefully guard from their classmates and friends.

Personality-wise, Kanata is depicted as a prudent, responsible, and caring young man. Despite the often chaotic circumstances of sharing a home with a sudden family that includes an alien baby, he frequently acts as the voice of reason. He is polite and possesses a good sense of humor, but he is also known for teasing Miyu about her mistakes, using this playful behavior to mask his deeper feelings for her as the story progresses. Even when he points out her flaws, he is consistently reliable, ultimately coming to her aid whenever she faces a genuine problem. His responsible nature is a key motivation, driving him to maintain order in the household and protect the secret of the alien baby, Ruu, who lives with them.

Kanata's role in the story is defined by his co-parenting dynamic with Miyu. Together, they navigate the challenges of high school while pretending to be a normal family for the sake of the telekinetic baby Ruu. Ruu, who can communicate telepathically, comes to call Kanata papa because he looks very similar to her real father. This responsibility forces both Kanata and Miyu to mature quickly, balancing their school lives with the demands of caring for a powerful and mysterious child. His key relationships include his bond with Miyu, which evolves from an awkward and forced cohabitation into a deep, romantic connection. A pivotal revelation comes when Kanata learns from Miyu's mother that he and Miyu were childhood friends, which helps him understand his growing affection for her. He also has a close, if often exasperated, relationship with his absent-minded father, whose departure sets the entire plot in motion.

Throughout the series, Kanata undergoes significant development. He starts as a somewhat solitary boy, popular at school due to his good looks and athletic ability, but his life becomes deeply intertwined with Miyu, Ruu, and the alien Wannya. The circumstances force him to become more emotionally open and protective. His development is fully realized in the long term, as it is revealed that years later, he marries Miyu and they continue to live at the temple, eventually having a daughter named Miu. Kanata is notable for his abilities as well; he is not only academically talented but also excels in sports, making him a well-rounded and admired student who has his own fan club at school.