As for your question of is this a BL or not, this is the most BL non BL out there. the writers, directors and pretty much everyone that worked on this show made it as if it's a BL, the actors of Ga On and Yo Han said they acted the parts as if their characters are in love with each other, the only reason this isn't a BL is because this was a big mainstream production and it's Korean, so they couldn't go all the way. I would recommend treating it like a Chinese "BL".
