Flower of Evil

Both drama are romantic thrillers.
Both dramas have married lead couple who are hiding secrets.
Both dramas revolve around uncovering the secrets.
But flower of evil, the marriage is well established meanwhile here it's not. Flower of evil is more crime based than this.

A series of crimes seem to hint at someone else at play. Who is the criminal and who is the good guy? Not everything is what it seems. Both MLs have personalities that hint at something dark but are they really evil? This cat and mouse game slowly unravels, past events are tied to the current ones to reveal who the real evil is behind these crimes.

Psychological thriller, intrigue and revenge. Moon Chae Won in the cast. Song Joong Ki is a brilliant, dedicated and affectionate student, until he meets the person who it would make your life hell. He is betrayed and decides to take revenge by approaching someone important in the life of the ex.However, he did not expect that he could develop other feelings for this person. Was the thirst for revenge stronger than love?

Both have the same male main lead and genre. Cops vs culprit is a huge theme as well. Great action scenes.

Every episode making you butt clinched and keep you guessing while also doubting your own theory!!

So recommended to watchh

Lee joon gi is the male lead of both drama, the similarity isn't obvious but you have a mc who frequently gets himself into trouble by trying to shoulder everything by himself, and female lead who worries/cries about him, and due to misunderstanding, she questions his love.

This drama has the similar story line with the other drama more like a adapted or Korean version the stor is alot more similar to eachother whereas it's the Phillipines version the original story camera from the japanese version

Both male lead have a psycopath serial killers as their fathers and being a psycopath son made them have some sort of psychology issue...then the female lead come into their live and give love to the male lead and that make them different and prevent them from following their bad father's foot step... both series show how the male lead overcome their issue with the love and support from their love one.

Both the dramas surprisingly has similar vibes and similar character development for Leads. Both the Male leads here on these dramas...think similarly!

They're suspenseful, crime-centered dramas that focus on the crime-solving process.
Both MLs are mostly emotionless men with a tragic past and ties to a serial killer.
The MLs change after getting into a relationship with a bright, stubborn female.
Both FLs have a job related to solving crimes.
Both dramas make you want to keep watching once you start.

IONTBO is definitely a much more romance based show and Flower of Evil focuses more on the crime/thriller aspect (as of ep 6). Both shows have dark characters with ambiguous morality and motivations. Childhood trauma/violence and its role in influencing adult behavior also plays a major role in both shows.

I don't know if it's okay to go by description only, but while reading about Undercover, I kept thinking back to Flower of Evil.
Both have a married couple with children, but the male leads have a hidden identity they've been keeping from their wives and others. They both have the female lead learning this identity due to their jobs spinning what they believed of their married life around, however the male leads still do love their wives and want to keep them and their families safe.

They both have similar concepts. Also, a serial killer related to the protagonist/antagonists.
In similar by they both related to law. Many of the characters both have secrets together. Both have a main chacater that you can't tell if they are good or evil.

"You only have one problem. You don't see yourself in the way I see you. I'll like you a lot from here on out. I'll be there for you. I'LL TEACH YOU EVERYTHING YOU DON'T KNOW. Then one day, things will change for you. You'd be surprised. " - Ji Won, Flower of Evil

The female lead in "The Smile Has Left Your Eyes" tells the male lead almost the same thing. and it sure hits so heavy when they both do! The male leads in both drama have really low self-esteem and keep pushing away the female lead thinking they aren't good enough or so they won't get hurt!

Both dramas are crime thriller dramas. Both are really influential for the viewers emotionally. In both these dramas, the male lead goes through a series of difficulties to uncover their past.