Aiko was a recruit of the ADA, they have been for ages, but no one knew what their gender was...so kenji decided to prank Aiko..and hit them in the back of the head..with...a guitar. Aiko groaned

Aiko: you hit me on the head with a guitar?!

Kenji: Y-y-your a woman?!

Naomi, dazai, ranpo, yosano, fukuzawa, junichiro and kunikida: oooooo