The cat burglar they’re trying to catch in every chapter is a master of disguise, so he kept hiding as other people. The thief leaves a card for the main detective character before every heist, warning the Detective/the police which item the would steal so that the main detective character would be there. Every time the blond thief reappeared suddenly, it was almost always him taking off his disguise (usually as another police officer, or sometimes as an innocent person). The cat burglar was stealing items in order to sleep with the detective, since he promised to give the detective back the stolen goods if he would fuck. Every time, he’d trick the cop into getting handcuffed (usually by kissing and drugging him) so the cop couldn’t catch him.
The backstory is that the Detective dude took care of this petty thief in his neighborhood named Arusa (or something like that, I’m bad w names), and the minute that the cop started showing the petty thief that he truly cared about him, the thief disappeared. It’s not confirmed, but it’s strongly implied that Arusa and the cat burglar the Detective has been sleeping with/trying to catch are the same person. The cop thinks he figured it out because they both had the same unusual birth mark, the thief knew the cop’s first name, and because the cat burglar didn’t actually steal anything (and was just using it as an excuse to fuck the detective). Cat burglar refused to admit it but that’s just the sort of character he is lol.
I'm too stupid I didn't understand anything