I'm not a yaoi fan but I wanted to give this a try because it looks funny and mystical... But damn chapter 1 and we already have someone biting ass and large penetrations, please add the hentai tag ?
By long-standing convention in the western fanbase, the "Yaoi" tag means NSFW with explicit sex (everything else is "shounen-ai" instead, even if it gets pretty kinky).
Pretty much no one ever calls or tags yaoi as "hentai", presumably because the audiences for hentai (almost exclusively boys, with exceptions) and yaoi (almost exclusively girls, with exceptions) mostly really don't want want the other's stuff mixed in with theirs.