Just for argument sake, I think it belongs with an H tag even though some may argue it's smut, which it also is. Reason being the mc of all this is the dick. Even if it's not colored in, everything is technically drawn as something under the H tag. They even got it down to a shape. Smut follows the lines of erotica where you never see shit even when they're heaving sex. Everything is implied but no real visuals to back it up. H is where you see the genitalia along with all the action. In this case, chapter 2 is a good example. If a blowjob, handjob, + cumshot is not H, then what is?
I'm not saying this is bad in anyway. In fact, this take and pov is very refreshing when you have like 70% of current updates under the rebirth genre.