Ideas

Use me

Tae had a disease. It was due to some mutation but he couldn't feel. There were no emotions in his life. But his parents raised him right. He was emotionless but sympathized with others and helped those he could help. But there was never anything from the heart. Even when his parents died, he was more worried about how he would survive than he was sad that his parents were gone. You could call him a heartless bastard but he had a heart. Duh! It had to be there for him to live. But there were no emotions. 

Then in high school, he met Jikook. They became rather close. Almost like best friends. Jikook were in a relationship so they were closer to each other than to Tae. Then they got a break and coincidentally, he was in the same university as Jungkook. But no jimin? reason, he found the love of his life. When Jungkook told him all that, Tae did not know what to do so he asked him if he could keep a secret and told him that he was emotionless so jungkook won't feel too vulnerable.

When jk hurt too much and seemed on the verge of collapsing, Tae did not want to lose anybody else. So he told jk to use him. That he cant feel so he'll let jk do whatever to him. jk is hesitant at first, but he eventually agrees. Their relationship is rather physical. Eventually, JK uses Tae so much that he does end up forgetting abt jimin or being able to bear it and not thinking abt dying every other day.

Somehow JK falls for Tae knowing that he would never feel the same. Cuz he didn't feel. SO he tells Tae and Tae being the person he is tells him that if JK wants to date him or smthn, he's down for it. Jk thinks for some days and researches on could Tae be cured and he can but the procedure has risks. So Jk changes his major and risks it all again. He joins a team in Harvard that are trying to cure it. 

After a few years, kook is 27 and he returns. Finds Tae cuz Tae lived at the same place. He was an artist who was recognized for his abyss like paintings that drained you. Tae under goes the procedure. 50 50 chance.

1- Tae recovers and obviously falls for Jk. Nobody can resist him. And Tae becomes child-like. Innocent

2- Tae recovers but there's some mutation due to which he becomes suicidal. And ends up leaving kook

3- Tae does not recover but Jk still accepts him. The love is one-sided but Tae makes more effort to keep it stable and lets Jk win and tries his best not to argue, which is not all that difficult for him. They get old like that. A bit toxic relationship, cuz Tae does not love kook