Dazai was an incubus. A male demon believed to have intimacy with sleeping mortals.

You, of course, didn't believe in that. It was just some story to make sure people locked the doors at night.

You had tucked yourself into bed, closing your eyes until all of a sudden there was a pressing weight on your chest. You opened your eyes to a demon sitting on you, a big smirk plastered on his face. An incubus.