Yuji Kaido is an average guy with a problem: he's sick, and there's no cure. Doctors simply don't know enough to fix the problem, but they can offer Yuji an amazing opportunity. After reluctantly agreeing, Yuji is cryogenically frozen until a cure for his condition is discovered. But things are very different when he wakes. Tokyo (the entire Earth, for that matter) is in ruins, consumed by merciless, insect-like predators known as the Blue. Pursued by the massive arthropods, Yuji is rescued by icy professional soldier Marlene Angel, a member of a military team assigned to recover "sleepers" like Yuji and transport them back to the orbital space station where humanity has taken refuge. As the Blue hunt them at every turn and team members start to die, Yuji and Marlene will have to rely on each other to survive and to escape from the planet.
This is an exceedingly well-made show. The Blue are interestingly designed and frighteningly portrayed, the characters are likable (well, the good guys are), and the storyline never bores the viewer. The general film "rules" about who can and cannot die (children are safe, noncombatants are safe, etc.) are not rigidly followed here, and the series is all the more suspenseful for it.
There are a few issues, like a small amount of nudity that can jar you if you're not expecting it, and an environmental plot element that can feel somewhat preachy at times. However, these aren't enough to justify taking away any more than one star.
Blue Gender has a dark tone and its fair share of violence, and is not for everyone. However, if you enjoy the genre, this is a visually and, I kid you not, emotionally appealing series that can be horrifying, exciting, and even touching.