I’m not very familiar with this trope but I find it interesting. An adult exploiting their childish characteristics to their advantage can quickly take a dark turn. (Which I like)

I can see that type of person trying to seduce another adult while acting underage to see how the person would react. Pushing their limits, to see if they are going to cross the prohibited line and succumb to their darkest desire.

I'm thinking about Chilchuck and Momo (JJK) especially.