The plot's surprisingly nasty, as if lots of conspiracy theories came true with sinister (inter)national governments. An organisation called UW has a monopoly over global resource distribution. Half the world's population is dead, civilisation is crumbling, food is short and there are allegedly terrorist organisations.
At the same time, though, it's practically hentai. A global pandemic killed all the men, except for a tiny handful in cryo-sleep because they had a certain disease. Our hero, Reito Mizuhara, is called "Number 2" because he's the second man with MK virus immunity to have been successfully revived. Now, for the future of the species, his job is to have sex with as many women as possible! Artificial insemination doesn't work, apparently. (I don't know if I believe this. At first it just seemed like an absurd anime contrivance for the sake of maximum sleaze, but having watched the whole season it seems more plausible as part of the conspiracy's big lie.)
Unsurprisingly, this show's a bit of an odd duck. Sometimes, it's implausible and stupid. Sometimes, if you're watching the uncensored non-TV version, it's obsessed with tits and arse. Sometimes, though, its characterisation is hard, nasty and uncomfortable. (The bits I fast-forwarded through because they're unpleasant are also the parts of the show I respect the most, because it was brave enough to make those choices. That doesn't mean I'd recommend the show, though.)
THIS SHOW IS HORSESHIT BECAUSE...
...of the characters.
1. Reito is an ego-stroke for the involuntarily celibate target audience, because of his nobility in refusing to have sex even to stop mankind from going extinct! (There's a girl he loves. Uh-huh.) In fairness, though, he is a lot more likeable than his fellow Numbers who make no attempt whatsoever to resist temptation.
2. Rea Katagiri is Reito's second minder, with the job of making him cause as many pregnancies as possible. When we first see her, though, she scares off two girls by accusing him of being a deviant who sexually assaults everyone he sees. This is such an absurd lie that you'll get annoyed at Reito for: (a) not correcting her, (b) not objecting to having her as his minder. He's one of the most valuable people on the planet. His word is law. Anything he asks for, he can get. If someone falsely and pointlessly accused you of being an attempted rapist, would you want that person in control of your life?
3. Underage girls. It's common in harem shows to have a token underage girl, because there's apparently an audience for it. Sometimes she's used for skin-crawling fanservice and sometimes she's just an innocent. This show maintains that tradition... TWICE. Numbers 2 and 3 both have a young girl among their associates, even though those girls were chosen for their sex appeal as a potential fuck-buddy.
...and the show's also horseshit because of some of the sexual content. It's basically inherent to the story, yes, but was there any need for Chloe to be wearing that stupid, stupid uniform in ep.9? And then later to be naked when reporting to her bosses?
...and other daft story points, e.g. the following in ep.6. There's unrest among the population. "Why not use Number 2? If we have him distribute rations, it will calm the people down." (No, it will be pointless and meaningless. You're going to prevent dissatisfaction among the general populace by having a pretty face doing a bit of food handout duty somewhere? Shut the hell up.)
BUT, ACTUALLY, IT'S NOT THAT BAD BECAUSE...
...of the characters.
Okay, the girls hardly ever make any difference to anything. They'll be introduced, perhaps with a character trait or two (e.g. Maria Kuroda's tendency to forget to wear clothes) that will soon get forgotten. The Numbers, though, are of interest.
1. Number 1 thinks the new world is fantastic and never wonders whether or not the girls he requests had much of a choice. He's completely cool with the death of half the human race.
2. Number 2 is a Noble Harem Protagonist in a genre where his cliched upright goodness makes him a species-endangeringly selfish bastard. (We're not meant to see him that way, but he is.)
3. Number 3 has the darkest arc of all. He starts out as a bullied worm who's barely capable of looking at a girl and is almost pleased that all those people died, because he'd had such bad experiences with them. He ends up embracing his role with creepy enthusiasm and choosing to help someone try to take over the world. He has one of his former bullies brought to school and chained up in his room, so he can have sex with other girls in front of her. Despite all this, though, he's not a bad person. He's nice, sort of. When he turns into a shit in ep.7, for instance, he feels bad and afterwards apologises. There's a teacher he's in love with.
His episodes are, though, an ugly, hard-to-watch study of what living in a hentai could do to someone.
As I said, the plot's genuinely okay. You'll have to endure lots of boobs and stupidity, but it is. Mind you, there's so much plot that these 11 episodes can't reach the end of it, so for instance we never learn the deal with Robotic Purple-Haired Minder. The show ends by setting things up nicely for a Season 2 that will surely never happen. Ever. Not in a million years.
Ultimately, though, this is an anime where a male hero is encouraged to have sex with everyone on a Planet of Big-Boobed Women. (He keeps refusing, but that won't stop them pestering him.) The show's target audience is narrow, to put it mildly, and you already know whether or not it's for you.