Shōta Ōhara, the second son of the Ōhara family, navigates elementary school life with below-average grades, having once placed second to last in his class. Standing 135 cm tall, his ordinary world shifts during a ninja game with friends when he discovers a mysterious egg at a tree’s base. Cracking it open releases Q-Taro, sparking bewilderment and frustration that gradually blossoms into a bond weathering occasional clashes but fortified by mutual support.

Initially concealing Q-Taro’s existence, Shōta eventually engineers the creature’s integration into his family. Sibling dynamics with older brother Shin’ichi blend camaraderie and rivalry, while classroom tensions simmer with classmate Yoshiko Koizumi, whose attention Shōta quietly seeks—a desire complicated by neighborhood bully Tsuyoshi Saigō, his romantic rival. Kizao Kiza fluctuates between aligning with Tsuyoshi’s teasing and exhibiting subtler antagonism than typical rivals in similar tales.

A twelve-year time skip reveals an adult Shōta reuniting with Q-Taro at a celebration, their contrasting aging processes—Shōta’s maturity versus Q-Taro’s eternal childhood—prompting Q-Taro’s bittersweet return to the Obake world to avoid disrupting Shōta’s adulthood. An epilogue fifteen years later depicts 25-year-old Shōta married, symbolizing his completed transition into grown life.

Adaptational shifts in the third anime series rebalance Shōta’s dynamic with Tsuyoshi toward equality, while core elements remain: academic struggles, alliances with intellectually gifted classmate Hakase, and camaraderie with Koike, a local ramen shop proprietor, anchor his enduring character journey.