Kokoros school is collaborating with another institution to establish a bazaar where they can sell or rehome unwanted items from their homes. On her way home, Elder Tama informs her that she and her Cocotama friends have won a trip to the Cocotama World. There, they witness how full-fledged Cocotama gods work. During this journey, Elder Tama requests Kokoros assistance in helping humans recognize the value of their possessions rather than discarding them carelessly. However, Tepple had secretly entered the Cocotama World with others and stole a vital acorn that unlocks the Happy Tree containing Happy Stars, the source of magic for their world. Elder Tama discovers this key is missing, prompting the Cocotama gang to search for it. She explains that mushrooms are emerging from discarded items due to negative energy emitted by these feelings of sadness. These mushrooms affect both humans and Cocotamas, but the latter can eliminate them only with the acorn and at a slower pace than how quickly humans are currently disposing of their belongings. Tepple utilizes the acorn to obtain a Happy Star, unintentionally causing a rift of darkness and an infestation of mushrooms in Cocotama World. As a result, Happy Stars begin spilling into the human world, draining all magic out. To save both worlds, Kokoro and the Cocotamas must mend Tepple's heart before darkness consumes the human realm.
The film screened alongside Tamagotchi Movie: Tanpen Himitsu no Otodoke Daisakusen! short.