Marshmallow and her family have come to Grandma's house to celebrate the New Year. Marshmallow meets a little mouse named Xiaofu, who is searching for a place of good fortune so he can enter the Eternal Mouse Kingdom and attend the once-every-twelve-years Lantern Lighting Ceremony. Marshmallow also wants to attend the ceremony. By chance, she obtains an invitation to the Eternal Mouse Kingdom, and so begins a wonderful adventure for the girl and the mouse.