I believe Sketch is probably a decent drama for Summer 2018. I really like crime/corruption dramas because they are usually realistic and are about something relevant in the society.

Sketch starts off with the normal good cop trying to save everyone with a fiancee who is kind of unlikable who happens to be a strict prosecutor. They're relationship was kind of awkward and there wasn't much chemistry but it was necessary for the story. Then we have another cop (Shi Hyun) who is working in another unit that is kind of not really accepted by the police force and they start their investigations on whatever she sketches due to her ability from her childhood.
Each case in Sketch is pretty much surrounding money, crime, killings that occur in the society. Some characters that were quite annoying from the being like Jang Tae Joon, I didn't understand why he was so involved in the killings besides the fact his sister ends up dying in an event. Some of the morals of the characters were quite messed up but it shows that were all not normal human beings.

The one character, I did feel bad about was Kim Do Jin, he was quite the loser from the start to the end of the show from his wife dying and him killing all these people under the command of Jang Tae Joon and Shi Hyun's brother.

I did feel that the character of Rain's from quite dumb because he kept on letting Kim Do Jin get away but if he was caught then there wouldn't be a story here.

I would totally watch season 2 if there will be one for the story and maybe Shi Hyun and Kang Dong Soo's relationship.

I would rewatch just to get a refresh of the story and recommend this show.