Hi! Siren is interesting, I should watch it. These are good mystery-romance dramas:
Kiken na Venus- a mysterious woman claimed that she’s the male lead’s missing brother’s wife
Tengoku to Jigoku: Psycho na Futari -body switch between a police officer and a suspect
Bitter Blood -father and son partnered as police officers, with a police woman as the son’s crush
N no Tame ni- categorized as “iyamisu”( “ew mystery”), dark and has an aftertaste. The lead actress, Eikura Nana, got married with the second male lead, Kaku Kento after co-starring in this drama :)