This is a weird series. But I appreciate the way it really goes for broke with a far-out concept, blending genres along the way, even if I do think it's just a mite too ambitious for a series of this length (four volumes total).
7 Billion Needles is a seinen series by Nobuaki Tadano that's loosely based on the 1950 Hal Clement sci-fi novel Needle. Never having read that book, I can only judge the manga on its own merits, which is just as well since I get the impression the two stories are actually very different. 7 Billion Needles revolves around a reclusive high school girl named Hikaru, who gets caught up in a cosmic struggle between two powerful alien life forms when she becomes the Earthly host for one of them. Forced to ally herself with Horizon, the benevolent being that has taken residence in her body, she must help him (it?) to pursue the entity called Maelstrom, a terrifying force of destruction. After some cat-and-mouse pursuit, several violent confrontations, and an insane body count, Hikaru ends up with both beings trapped inside her, where admittedly they do much less damage to the planet, but where they're starting to drive poor Hikaru crazy.
Yet the truly crazy thing is that all this insane stuff actually ends up normalizing Hikaru's personal life in unexpected ways. She starts to come out of her shell, form real friendships, and even heal past emotional trauma as a result of her associations with Horizon and Maelstrom. And that's the thing I really like about 7BN, the way Hikaru's family and social life is woven into the bizarre sci-fi concept. I dig that.
Unfortunately, the artwork's a weak point (mostly serviceable, but occasionally muddled and confusing) and the pacing is uneven. There are so many elements at play here, and none are really fleshed out or given any breathing room. I do like the story, even if the execution is lacking, and I'll be checking out the fourth and final volume when it's released.