Close yet far. The evil twin tortured a puppy to death and tried to kill the MC; I don't think he's redeemable. He's more like Dio from JoJo. And the MC, even with his amnesia, is having sex and is in love with the ML, and it's the ML who keeps his distance for fear of the MC ending up in the hospital again. More than the romance, the villain's power amd misstery is interesting. I don't understand how the MC's mother, knowing what he did to her son, allows him to be near the psychopath and contributes to his manipulation.
Is this also the same author as "A Guy Like You," right? If I remember correctly, there wasn't a love triangle in that manhwa, but since I read it 10 years ago, my memory might be failing me. My comparison to Dio is mostly because of the manipulation of Jonathan's father and the death of the puppy. I've never been able to get through the first arc of JoJo's because of that death.

This story is about pretty twin brothers and cute little twink mc. Our mc got hurt in the head and forgot about the green flag twin then thought evil twin is his savior. And the green flag twin will follow mc until mc makes out with the evil twin. When he finally gives up on mc, mc realizes his own feelings and starts chasing the green flag twin back. That's when the evil twin starts to understand about his own feelings for our mc. And then the green flag twin and mc will end up together. With some scenes of evil twin turning a good big brother and left heartbroken.