SPOILERS
Won-Il also made mistakes and that's what helps him fit into this story so well imo. He's a helpless bystander while also being the closest person to Hyunjae. He decided to put up a front to stay close to Hyunjae when Hyunjae was too insecure to accept him, digging himself into a deeper hole surrounding Hyunjae. Won-Il is self sacrificial and that is his own misery. He let Hyunjae stay with his kidnapper more than once, and repeatedly mentions that he's entirely weak to Hyunjae's will, even if it's irrational. The peak of his "role" was when he was tied up and nearly forced to wake up to two dead bodies hanging. He is deeply intertwined into their story, he's got some problems too LOL

I guess it got a high rating because it’s psychological so it wasn’t supposed to have a fluffy ending
But dang why make the red head suffer in the end too. The MC and ML are the ones with psychological problems (MC not being able to have a healthy relationship and pushing away those close due to fear, ML’s whole living in fiction thing caused by his mother) just let them have their problems keep the red head out of it and give the man some peace