wait i didnt know that theres s2, i couldnt find it tho
S2 start after the seme left and the uke got flashbacks of his childhodd.
I haven't read the whole story in a while but the change was intentional and was symbolic of the change in their relationship and in Woojin's perspective. Before he becomes attached to Hwon, his memories are distorted and he's disinterested in his own life, hence the grey scale. As his love and attachement grow, color is introduced. It also serves to enhance the mystery of Hwon's identity (because Woojin couldn't remember who the beggar was and who his friend was). And the reason you felt Hwon's personality changed was because your perspective around his motive changed once you were introduced to new information. Hwon is just as manipulative and violent as the first season, but he changes tactics (i e. his aggressive approach) to try to lure Woojin back in. A lot of the changes in characters is simply character development in response to changing situations. Not trying to dismiss your perspective!! just trying to introduce some possible symbolism that could influence the perception of the story bc I love this story so much haha.
I really like season 1, but season 2 felt like a completely different manga. The style is changed, and the characters personality and action felt very different from season 1.