How is that possible? Space hyung was older than him....
Did he shrink or something?
He fell thru some sort of a time rift so he kinda regressed.
I HAD A FEELING THAT IT WAS HIM
It's a paradox, to save Joonmin(ML) while they were inside a gate against their enemies, Yugyeol(MC) jumped inside a rift on the gate causing him to travel back from when the gate was still active. That was when he met the 15 year old Joonmin, at that time Joonmin was blind so he didn't know what "Space" hyung looked like and just felt him. Beaten up and wounded from his recent fights, that's how he ended becoming the "weak and sickly" Space hyung that Joonmin took care of. Two and a half months passed, that's when the imprinting happened, and the very events that caused Joonmin and Space hyung to get separated happened again.
The older Joonmin jumped into the rift, and saved Yugyeol. That's the reason why our younger Joonmin couldn't find Space hyung no matter what, he's a time anomaly. Then you'll ask, but if Yugyeol IS Space hyung, why did Joonmin's body still reject him? He wasn't supposed to actually, his body was supposed to recognize his imprinted guide even if he technically wasn't the Yugyeol he imprinted with. It's just because Joonmin is an S class Mental Esper, he rejected any kinds of possibilities and strongly believed his hyung was still out there—thus his own abilities made him reject the young Yugyeol.
It's a very beautiful story I highly recommend you guys to read the novel, because Joonmin never ever EVER laid hands on Yugyeol, he never even kissed him until the ending when they were actually together. This manhwa is kind of ruining his image :/.
Yugyeol (MC) IS "Space" hyung/Uju-hyung