hentai literally translates to "pervert" so as per saying "H-stuff" it just basically mean "let's do something naughty/perverted" in much shorter term "Let's fuck"
Then it should've said plainly "Let's fuck"
same thing
If you hadn't realized, H in Japanese has the same sound as Ecchi, so it can basically mean " Let's do Ecchi-stuff! " but shortened to H-Stuff.
I don't think Hentai and H-Stuff correlates. It just so happens to start with the same letter.
I keep seeing this phrase used a lot in BL... What does H-stuff mean?
This isn't about hetero relationship so I don't it means "Hentai"-stuff.