Maru is mochi who enjoys spending time sitting on peoples' heads and talking to them. Although he isn't particularly adept at conversing with them, he makes up for it by being a good listener.
Maru had just been a mochi offering given to the Goddess Amaterasu. Upon descending to Earth, Amaterasu, instead of consuming Maru, bestowed upon him the gift of life. And thus, he spends his days wandering the world around him, always looking for something new to do each day.