Mature
The little boy laughed obnoxiously at the computer screen. “Ha ha, you’re writing a Mature story!”
“I wouldn’t expect you to understand.”
“You’re naughty!” The boy yelled, pointing and laughing.
“And you’re immature.”
“Nuh-uh!” The boy contradicted. “Maturity only matters if you believe in it!”
“That doesn’t make any sense!”
“I wouldn’t expect you to understand.” The boy smiled smugly. “You’re immature.”