Kunikida and Dazai were dating,and partners in the ada. Their relationship was on good terms,even though they fight some times. Kunikida and Dazai had sex,on multiple occasions..

Expect this time was different... When I was giving you love bites on your thighs,it hurt more than usual?... So you naturally picked me up and threw me on the bed,and straddled my waist,while you sat on my lap... You opened up my mouth with your fingers,to find out that I had fangs.... You didn't really care tho... Since you had seen me in a lot of situations...

"Hmm. Interesting.."

Kunikida said, as he feels my fangs with his fingers.