Yotsuba Koiwai, a lively five-year-old, views the world as a wondrous playground filled with exciting discoveries. Upon moving to a new city with her adoptive father, Yousuke, she eagerly explores her surroundings. Through playful escapades at the local park, the Koiwais befriend the Ayase family, consisting of three daughters with distinct personalities. Despite initial skepticism, Asagi, Fuuka, and Ena are drawn into Yotsuba's spirited escapades. From mastering a swing to brainstorming unconventional solutions like cooling the planet with air conditioners, Yotsuba's boundless enthusiasm both captivates and exasperates those around her. With the support of Yousuke, the Ayases, and newfound companions, Yotsuba revels in everyday escapades, cherishing the simple joys that life offers.