Comet Robo is a place where robots who can make anything live. The robot girl who lives on this planet, Roboly, is always the best at what she does. However, she learns that there is only one "important thing" that even she can't make, and leaves Comet Robo to find it. During the journey, Roboly and her partner, the little robot bird Koto, pick up a gift box containing a nice music box and come to Anpanman's world to find the owner.

As she meets Anpanman and spends time with him, she notices that her chest feels "warm" for some reason. While wondering about her first feelings, Roboly gradually deepens his bond with Anpanman and friends.

At the same time, Baikinman invents the strongest mecha "Roboking" and goes on a rampage in Comet Robo. Will Anpanman and friends be able to protect Comet Robo from Baikinman? And will Roboly be able to find the "important thing?"