Wrong tag Update: fixed!

I don't blame you for believing that the anime is gay, though it is not. Yes, studio Bones made the opening gay as hell. But just because the studio framed the anime that way, and that many viewers may misunderstand because they are used to thinking, "oh, 2 male protagonists, vampiric setting, must be gay", means that the actual content should be tagged as BL. Tags are supposed to be factual and objective, separate from viewers' headcannons.

This anime is about two gay vampires (You can understand that from the first episode).

I think that there is some misunderstanding. Vanitas is a human. He states so in the very first episode. His character setting is human in the manga.

BL tags are used when there is explicit romantic feelings between two guys. There isn't anything like that in the manga. In fact, Vanitas believes that he loves Jeanne. Judging by how a season 2 has been announced, Bones is likely going to adapt the manga faithfully. We can say this safely for season 1, at the very very least.

Furthermore, in Aniplex Online Festival 2021's Making of "The Case Study of Vanitas", there was an interview with the producer of Vanitas no Carte, Naoki Amano, who states that

The Director wants to portray the style of the original work to the viewers as much as possible for this title.

Aniplex has made the recording of the Festival available on Youtube until July 11. You can find it here: https://www.youtube.com/watch?v=YNjC7w46E0k&t=4s

Making of "The Case Study of Vanitas" starts at 3:01:19. The above quote is from 3:05:48.

Given that there is a season 2 and that the director wants to capture the original work, the anime is likely going to follow the manga where there is no BL instead of cooking up something that dives into BL.

I am not bashing BL lovers, nor am I saying that everyone should be "into such things". I'm just a sincere fan of Mochizuki and want her works to be described accurately. I hope you can understand where I come from.