Harvestella takes place in a vibrant and colorful world where four massive crystals known as "Seaslight" create a stable transition between the four seasons. The adventure begins when anomalies in the Seaslight appear and generate the "Quietus," a death period that occurs between the naturally occurring four seasons. During the Quietus, crops wither, and people cannot venture outside, and disturbingly, these seasons mysteriously grow longer each year.

In this life simulation role-playing game, players will grow and tend to crops, use ingredients for cooking and crafting items, and venture into the overworld, which dynamically changes with the seasons, to visit different towns, interact with the townsfolk, fish, and much more. Players can choose from various jobs such as fighter, shadow runner, and mage, and team up with their group to explore dungeons to uncover the origins of the world as well as the truth behind the calamity along the way.