Inseop is really good at using good opportunities. Gijeong's brother is lonely and depress? Tell him to make a journal Abt his feelings and later stage his murder as a suicide so he can own gijeong for himself, but that was the first plan.Because even when kiseong said himself that he will commit suicide, he didn't. He then told kiseong to kill his cousin so he wouldn't be an "insect" anymore, My guess is that he'll either sell the brother out to the police with whatever evidence he finds or that because the brother already has a deteriorating mental head and he killed someone, he might actually just commit suicide and that would be a win for inseop. After the cousin's killing inseop calls gijeong and asks her to help move the cousin's body, he's tying himself to her through the murder of her cousin. They both share something in common, they'll share a secret, and it's them hiding the cousin's body.
Also does anyone else think that inseop will be killed by gijeong after finding out who he truly is? It's foreshadowed. Gijeong kills a mantis cuz the mantis eats the worm. the mantis is inseop and the mantis loves the flower but the worm eats the flower destroying it's leaves so the mantis eats the worm. Inseop loves gijeong because she is radiant like a flower.
Ngl if that does happen I still low-key would like ms.go and inseop to at least have one panel of them sharing a kiss... I would actually be so happy, seeing ms.go all happy and Inlove would be refreshing for her character because we mostly see her get beaten down by others so it would just be delightful if she her love develops for inseop and knows it's "reciprocated" and she would be very contented. (But after that she would feel a nuclear bomb explosion of betrayal from inseop and it would be peak writing)

Even though we know inseop is smart, one of the noticeable traits he has is when he makes a mistakes because he couldn't believe that he didn't thought of it before. Like when he texted gijeong that she was innocent and then later on posted about her involving the detective so she would inevitably be fired, he didn't expect gijeong to cut ties with him I think he expected gijeong to go to his office again to ask for help so he was very shocked that she decided to cut it with a "thank you for everything" and that time when he killed the mom just so he could have a reason to see her, you would think that it would be logical to at least come up with a reason for being there but he didn't, he didn't even come up with one immediately and decided to switch the topic.