The instruction manual for the Yasashii retells the story of the Tamagotchi Planet getting drunk, forcing the Tamagotchis to flee to Earth. Nearly two years after the incident, it's time for the Tamagotchis to start returning home. Professor Banzo, who invented the first Tamagotchi toy for them to live in, still wanted to experiment on making a more comfortable environment for the Tamagotchis to live. He and Mikachu eventually create the Yasashii, a larger, more comfortable home for the Tamagotchi to live in with greater ease of providing care.

The Yasashii Tamagotchis, also known as "YasaTamagotchis", are Tamagotchis that were born and raised on Earth. Thus, they only know about Tamagotchi Planet based on stories from older Tamagotchis who had lived there. The YasaTamagotchis are excited to return to their home planet for the first time.