Little Goku just running around with that dragon costume being the little scamp that he is. I like the coloring and the shading, too. The dragon costume looks cute and cartoony. The shadow looks well-done, too. Nice job overall.
It's not so difficult, there are lot of simple style. In that artwork I used a tool which seems like watercolor but is not. It's watercolor for kid like this [link] or this [link] ^o^ The quality is less fluid than real watercolor and it creates some powder when it dries so we need to fix it with a spray.