Santa Company is a worldwide organization dedicated to delivering presents to children. Santa Company's elves—known as "tonttus"—aid several Santas every year by wrapping presents, raising reindeer, and helping with deliveries. Mint Rondo is one of the many new tonttus arriving at Santa Company's tropical island office. Following in her older brother's footsteps, Mint begins training alongside her friend, Thomas Dou, and rival, Noah, to eventually become a Santa herself. Unfortunately, her clumsiness causes her to fall far behind her peers and into her brother's shadow.

One day, while sitting on the beach, Mint, Thomas, and Noah discover the biggest threat that Santa Company has faced yet: ocean pollution! With the accumulation of litter going unnoticed, the growing hazard will soon endanger the surrounding ocean wildlife and the members of the Santa Company. As trouble looms over the horizon, Mint might just be able to clean up her act and save everyone on the island in time for Christmas Eve.