Gong Yoo and Park Bo Gum are amazing.
I know I lot of people had problems with this movie, but I thought it was incredibly well acted and incredibly sad.
I don't love all the violence but when you get through to the end you understand the pressure that has been building up in Seobok, and the narrowing of his options, and the violence comes out of that.
GY and PBG are two of my favorite actors and their work in this movie is beautiful. You see the subtle changes in their relationship and their growing understanding of each other, so the loss at the end is devastating.
The story is just a vessel to hold the relationship between the two of them. Their discussions about death are given higher stakes because of what they know about themselves. And their perspectives shift because of their relationship.
The only really important supporting character is the "mother" figure. Jang Young Nam doesn't have many scenes, but she conveys the character's intense pain in every moment. This actor never disappoints.
The "bad" guys' behavior isn't justified in the writing, so those characters are boring. But Seobok and Ki Heon are absolutely at the center of this story, and I had no problem focusing on them.
This isn't my usual taste (I like romcoms and sageuks), but because of GY and PBG's performances, this movie will stay with me for a long time.