Basically, this is a normal setting for BTS, except that there are soul bonds included. I describe a soul bond as a romantic, unbreakable bond between two people; it disregards race, sex, gender, and supposed sexuality of said person. Age will obviously be taken into account because pedophilia, molestation, and pervertedness is NOT okay.
The soul bond— which will obviously be between Yoongi and Taehyung— will occur much later in the story.
Anyway, Taehyung is behaving way out of character for him, and when Yoongi finds out that he is secretly composing a song with nobody else’s help, he thinks that’s the reason why he’s behaving oddly. But it’s not.