he goes to confront kdj once he learns of the truth of the matter from hsj, only to find him in front of a mirror clad in lacy, white lingerie that clearly isn't being worn properly.

yjh finds out about this since kdj isn't exactly subtle about anything
especially when his attitude takes an almost concerning turn with his attempts at setting up a,,,'sexy' mood?
(he is absolutely the type to try and set up a 'oh no im stuck in the washing machine' plot)

he thinks the relationship is suddenly on the brink of collapse and that he needs to save it by seducing yjh
he quickly turns to acquiring more research material (erotic novels) and clings onto their every word to save him from his selfmade crisis.

in reality its because yjh knows that kdj, even after a month of them dating, isn't ready for something so advanced and is still struggling to accept they're even dating still.
kdj wont ever come to this realization of course

ofc he comes away with all of the wrong impressions and even more confused than before.
thinking he needs to have sex with yjh as some sort of 'initiation rite' for the relationship, kdj now worries that he's not 'sexy enough' since yjh hasn't really made any moves on him