History 3 trapped is less intense and more comedic, however, there are definitely similarities between the two. Both have one character that is quite firm with their beliefs and morals who falls in love with someone who challenges these morals. Also in both shows there is a heavy presence of crime and police officer main characters.
The vibes it gave has similarities like baddass characters, strong male lead, fighting moments and crimes-story. Even the path is different ( H3-trapped is more police-mafia lovestory & Jack & Joker is more debt collector - pro stealer lovestory ) but still they gave mafia vibes with enemy to lovers plot
This was the first BL drama I watched and really liked a few years ago. I know KeiXYaku is not romance genre like trapped and focus almost completely on investigation part but the similarity between Police and Gangster working behind the back for the mysterious death of someone’s close to them is undeniable.