for me, I thought it was obvious so no need for an explanation. i'll proceed why I think it it is though,
The Art style in general looks premature (sorry) it resembles art drawn by most middle-schoolers where the head often ended up looking like an homo erectus; eyes positioned rather high, short and fully flat back. The lips are thick, just like how kids trying to draw lips as realistic as possible but ended up looking like it had a lip injection.
I also notice how the characters expressions here are redundant & limited. The eyeshadows sometimes looks overblown and the overall coloring lacks depth.
Though, all this is understandable as it is an early work of the creator and I think it is the result of them trying to avoid from the generic 'Manhwa BL Look'
the art sucks