The story begins with Tets Akilea, a seemingly ordinary human high school student, finding a discarded convenience store bag. Inside, he discovers a small, reptilian creature that makes a "kyau" sound. Initially mistaking it for a kitten due to a story he'd heard, Tets realizes it's a lizard. Despite his mother's reservations about its diet and potential toxicity, Tets decides to keep it, naming it Gonsuke. He prepares a habitat for Gonsuke, but the creature quickly proves to be more than just a lizard. Gonsuke escapes its enclosure and is found in the mouth of the family's cat, Pon, before being rescued by Tets's grandfather, an Orc.
Tets's family is a mix of fantastical ancestries: his mother is a half-god, half-demon, his father is a human with a heroic past, his grandmother is an Orc, and his grandfather is an Orc. Despite this, Tets considers himself ordinary. Gonsuke demonstrates an unusual ability to manipulate its tail, transforming it into a hand to open its tank lid. Tets is amazed, speculating that modern lizards might possess magic. Gonsuke then exhibits a surprising affinity for Pon, the cat, even falling asleep on its head.
A few days later, Gonsuke sheds its skin, which Tets's grandmother, believing it to be from a snake, keeps for good luck. Tets notices Gonsuke growing and developing bumps on its back and head, resembling horns. He jokingly suggests it might be a dragon, a rare and expensive pet. His grandmother warns him to be responsible. Gonsuke also displays intelligence by watching videos on Tets's phone.
Gonsuke continues to grow rapidly, eventually reaching the size of a large dog. It learns to use the litter box independently, possibly taught by Pon. Tets's mother suggests taking Gonsuke for walks, and they acquire a dog collar and leash. During a walk in their rural village, an old man mistakes Gonsuke for a large turtle. Tets explains Gonsuke was found abandoned, and the man shares stories of people abandoning turtles. Gonsuke shows interest in the man's dog, but the dog is wary.
Tets's phone buzzes with a social media notification. He reflects on the societal norm of having a "status" system embedded in people's brains from birth, which displays their abilities and allows for internet connectivity. Tets, however, has not undergone this procedure due to his lack of illness and his parents' reasoning that it was too early. This makes him an outlier among his peers.
While at a convenience store with his friend Masa, a Dark Elf, Gonsuke's true nature is revealed. Masa, who has the status system, identifies Gonsuke as a "rare of rare, five-star rare divine dragon." Tets is shocked, having believed Gonsuke was just a lizard. Masa explains that Gonsuke is female and that dragons are highly prized pets, often seen as status symbols for the wealthy. Gonsuke's unusual behavior, like trying to drink Tets's soda and then using its tail to damage the convenience store's parking lot, leads to an apology and a purchase of Gonsuke's favorite food.
Later, Gonsuke drinks Tets's grandfather's beer and is temporarily banished from the house. Tets learns that dragons can consume high-purity magic, or "divine energy," which is incredibly rare. He also considers the possibility of Gonsuke being stolen due to its rarity.
Gonsuke continues to grow and develop, even learning to mimic actions like bowing and drinking sake. The family discusses the challenges of Gonsuke's size and the need for advanced magic training, specifically transformation magic, which no one in the family can teach. They consider asking Tets's older sister, Takara, who is skilled in magic.
Tets's sister, Takara, contacts him, having seen a viral video of him with Gonsuke at the convenience store. She scolds him for not telling her about his new pet. Gonsuke, meanwhile, shows a fondness for watching videos on Tets's phone, even operating it with its tail. The chapter ends with a confrontation between Tets and Gonsuke over the phone, which is interrupted by their mother, who punishes them both.
