Good hentai and funny. First off the title says it all, well the "invisible" part is right but the "stud" part is wrong" It's the story of a guy who finds the Holy Grail, the Fountain of Youth...actually he finds an item that turns him invisible (so it's just as good). Dont worry about the story, the concept is all that matters: a man who gets no respect from women who can turn invisible. You can really connect with the protagonist. Think about it, what would you do if you could turn invisible? Fight crime? Save the world? What is this a comic book? No you'd use this power tospy on women in the bath house, haunt an all girls school, get laid, rape the girls who were mean to you...
Basically, every sex scene is a rape since non of the women are actually concenting, but it's not those cruel kind of rape that hentai are infamous for.

There are good fan service aswell, at some point all the words stop and you just enjoy the fan service. The camera angles are very good, the animation is not too detailed and it's uncensored.