
HE IS STILL HYPNOTIZED!!! IS IT REALLY NOT OBVIOUS?!
Being under hypnotism doesn't necessarily mean doing whatever the hypnotist wants. It can be as simple as "From now on, shitting under the shower is normal for you" and that's still hypnotism, even if the recipient is otherwise normal and functional.
In this case, he is still hypnotized into subconsciously thinking sex between brothers are normal. I mean, come on, it's pretty damn obvious. He may not be under heavy hypnotism like in the 1st season, but he. Is. Still. Under. Hypnotism.

"Hyung" (2nd "ML") was originally supposed to be Hangyul's (MC) life partner; his red thread was connected to Hangyul's. He could've mended it in the flashback if he reconnected with Hangyul, but he fell in love with Hangyul's brother instead. So now, die to the bad karma he accumulated, his red thread, which was only cut back then, is completely gone; meaning he is absolutely incapable of having a love life forever....
UNLESS he somehow someway cuts Hangyul's connection to blonde guy (forgot his name LOL). THEN he would regain his red thread again. Now, who that red thread would get connected to depends on him. It COULD be re-connected to Hangyul, but judging by how the story goes, it would probably be connected to Hangyul's brother. ASSUMING he would be able to cut it. But he probably would, cause I don't know how else the story could move forward.
"Kunigei" is a play on words. Although it's written in katakana (クニゲイ), the kanji for "Kunigei" should be "國藝" which is really just the shortened version of the manga's title "大國大学藝術学部映画学科" (Okuni Daigaku Geijutsu Gakubu Eiga Gakka). And it can also he interpreted as "Kunigei" as in "the Gay of Okuni University.
Why am I telling you this? Well, as far as the pun is concerned, the BL undertones in this manga might as well be intentional LOL.