Kotarō Kawaii is the main protagonist of the story. He is a second-year middle school student who created a living slime named Puniru when he was in elementary school. This event shapes his daily life, as Puniru has been his companion for seven years. Despite his ordinary appearance and desire for a normal existence, his life is far from typical due to Puniru's antics. As a child, Kotarō experienced a deep trauma related to his fondness for cute things, which he believed was not appropriate for a boy. This causes him to hide his genuine feelings and refuse to openly acknowledge Puniru's cuteness, even though he secretly finds her adorable. He is often depicted as a tsundere, reacting with embarrassment and frustration to Puniru's transformations and behavior, yet he cares for her deeply. Kotarō's primary motivation is to lead a normal school life. He has a crush on his senior, Mami Kirara, and struggles to navigate his romantic feelings while dealing with Puniru's chaotic presence. His internal conflict between his childhood attachment to Puniru and his desire for conventional teenage experiences drives much of the narrative. In the story, Kotarō serves as a straight man and narrator, whose reactions highlight the humor and absurdity of the situations around him. His key relationship is with Puniru, whom he created; their bond evolves from that of a creator and creation to a close friendship with underlying romantic tension. His crush on Mami Kirara provides a love triangle dynamic, and he also interacts with classmates such as Go-yan, the eccentric teacher Hiroshi Mado, and rival Alice Okanega, who further complicate his life. Throughout the series, Kotarō undergoes development as he gradually comes to terms with his own feelings about cuteness and his relationship with Puniru, learning to accept parts of himself he once rejected. In terms of abilities, Kotarō possesses no supernatural powers; his role is primarily as an ordinary human who must navigate the extraordinary circumstances created by Puniru's existence. His key traits are his emotional resilience and his capacity to care for others, which ultimately define his character.