The principal adores his grandson very much and asks the Sket-dan to prepare a picture play to entertain him. They decide to base the story off of Momotaro, but change things up from the usual... Afterwards, he asks them to play with his grandson for an afternoon, but the kid doesn't seem interested in having fun at all.
There is nothing naughty 
about True Heart Graffiti!
¡No hay nada malo en True Heart Graffiti!
¡No hay nada malo en True Heart Graffiti!
Não tem nada de nojento 
no True Heart Grafitti!