After I Transmigrated into a Book, I Became an Online Gigolo

A transmigrated into a book and became a little duck. And what's more, it was made of porcelain. He couldn't even pass for a real duck! All he could do was tag along with a poor little kid, making ends meet and giving the taciturn child advice so he wouldn't get bullied. Other people got a wise old man living in their minds; he got a little duck. When the poor kid got beaten up, the little duck taught him a hundred ways to put a sack over someone's head. When the poor kid got insulted, the little duck taught him a thousand ways to make cutting, sarcastic remarks. When the poor kid got mistreated, the little duck planned ten thousand ways to get revenge for him. Later, the poor kid grew into a peerlessly beautiful and powerful demon lord who could turn the clouds with one hand and call down rain with the other. But the little duck was nowhere to be found. Demon Lord: What a lousy world. Let's destroy it. [The protagonist is called A because I'm terrible at coming up with names and haven't decided what to call him yet.] Theme: Even in adversity, keep your heart turned toward the light