Saru to Momo

Saru to Momo summary:

A celestial monkey named Gokuu, who was given the title of Saiten Taisei, is in charge of the Celestial Peach Garden. However, he tends to only eat the peaches and do nothing else. After not being able to find any other ripe peaches to eat, Gokuu tries an unripe one. To his dismay, it doesn’t taste the same and he throws it away from Heaven. This peach rolls and rolls until it eventually lands on Earth, becoming a human itself… And so…fifteen years on Earth passes in the blink of an eye.