Our hero, Narifumi Hosokawa, is preparing for his high school's culture festival with the Kadomori twins. While everyone is distracted, Shizuku decides to open a mysterious gate through the use of magic and travel to an alternate world. She has broken the oath of her family's heritage, as to protect the Black Gate from those who seek the enormous power that lies within the world. The remaining defenders of the Black Gate, consisting of female students and a female teacher, must travel through to the other side and return before any distruptions come to either dimension. However, Narifumi accompanies the group and Shizuku is waitingfor them with some new allies.

When it came to the sex, Black Game gave me the worst feeling you can get from a hentai. Boredom. I shouldn't be bored during a scene of two people fucking. And that's when the sex is even happening to begin with. I don't even know how you do that. There isn't enough time with any of the girls to at least give them stereotypical traits for me to jerk off to to begin with.

It also doesn't help that all of the good animation and anything even remotely interesting happens in the OP, which only lasts 30 seconds, and contains no sexual content. So you have to deal with a bunch of mediocre animation to go with your bad sex scenes knowing full well what good animation could look like for this OVA.

Also, the previously mentioned mysterious gate is blatantly the Stargate from the Stargate series. It's not even a homage, it's just a blatant rip-off. They probably put it in knowing that they could get away with it, because 1) Who the fuck is going to admit that they watched something like this to try and get money from a blatant Copyright Infringement, and 2) The people jerking off to this aren't going to care either way.

The dub is forgettable ans awkward and all around awful, and it has even worse dialogue. "You're wet." and "I'm going to move it now.", the same insufferably annoying filler dialogue. There's even forced foreshadowing during a sex scene – "I don't need your protection, I'm a big girl now." What a weird thing to say during sex.

And every other line out of out main protagonist is "Huh? What? What is going on?", like a complete doofus.

With generic spank material that's been done better in the years both before since, and the fact that the rest if it is just unappealing, Black Gate just isn't worth it.