Life is love. Love is warmth.

Kyungsoo is always cold. The heat is never too hot. He hates the cold. He is already so sick in his mind that besides he doesn't need to feel that way physically.

Actually, Kyungsoo doesn't hate the cold itself ; he hates being alone, being unable to feel others' warmth.

Jongin is the warmth.

During late nights, Kyungsoo would ask Jongin if he could sleep with him. He always find the younger half undressed, laying next to his couch on his bed, almost dead because of the training. And because of his painful body, Jongin has trouble falling to sleep, just like Kyungsoo.

Jongin is too tired to speak at those hours. He would just let out a deep and sleepy sigh while lifting his couch up lazily to let Kyungsoo in.  Right after, Jongin would hold tightly his cold hyung.

Kyungsoo is a kind of anesthetic for Jongin.

Jongin is so damn warm, his skin burns Kyungsoo's.

Next to Jongin, Kyungsoo feels so dead. He's like a dead body ; pale, cold and empty. Being cold is like being dead, Kyungsoo thinks. He's scared of death. He feels alive when he listens to Jongin's soft heartbeats. Those signs of life lull him. When he is about to fall asleep, Jongin lets go of him once he cooled off, leaving the elder cold like never before. It has always been like this.

Jongin is the fire which extinguishes easily. Kyungsoo is the ice which doesn't melt.

Maybe Jongin isn't enough warm for Kyungsoo. 
Maybe Jongin’s love isn't as strong as Kyungsoo's.