While I do enjoy a good post-Apocalypse setting, there's very little that can compare to a good disaster story, showing us the apocalypse itself rather than the way society copes with it. Surprisingly, this is a less common type of story than I initially thought, but I enjoy it immensely when I can lay hands on it. Any type of disaster can work, and I find that the weirder it is, the better. I've covered Lives in a different article, which isn't a series that most people would want to read, but it does have a strange disaster afoot. The three below were some of the only other series I could come up with, but two of the three come highly recommended.
Dragon Head - Minetaro Mochizuki (10 volumes)
This topic exists because I wanted a reason to talk about Dragon Head. It fits neatly into the horror category, but works its best magic as a disaster story. It starts off with a train full of students in an underground tunnel that... suddenly collapses on itself. Everybody is killed except for Teru, Nobu, and Ako, who scavenge for meager supplies and wait for help to come. Except no help arrives, and they find themselves down in a dark tunnel with next to no food, no water, no link to the outside world, a diminishing light source, and a ton of dead bodies that begin to decompose in the rapidly rising temperature. Eventually, Teru goes mad and paints his body with blood and begins stalking Nobu and Ako, who flee through a series of air vents from the boiler-like tunnel. When they reach the outside world, things aren't much better. Something terrible has happened, and they don't know what. There are no cars, no people, no radio broadcasts, and no evidence of anything except a terrible disaster of indeterminable origins. The first three volumes cover the tunnel and their escape, and those are three of the scariest volumes of manga I've ever read. The following seven volumes are Teru and Ako's trek back to Tokyo, running across a great deal of survivors in various stages of sanity and precious few clues about what's going on. Supplies are scarce, and they also stumble across some sort of project that appears to be lobotomizing the survivors. The rough, inky, and somewhat realistic art serves the story well, and it's a non-stop action series that keeps you turning the pages for all ten volumes. It truly is an amazing piece of horror fiction, and I would highly recommend it to anyone into the genre. The disadvantage is that it's long out of print, having finished its run in 2008 at a defunct publisher. But none of the volumes I looked at were valuable, so you should be able to get a used set on the cheap.
Limit - Keiko Suenobu (6 volumes)
The disaster in this story comes when a bus full of students on a class trip pitches over a canyon and all but 6 of the girls are killed. The canyon is blocked on all sides, and the girls believe they won't be missed or rescued for almost a week. In the meantime? The class outcast gets ahold of the scythe they were to use in their camp, goes crazy, takes all the available food, and decides she is in the leadership role. A current, short series, I've only read the first volume, but it does a good job of creating a tense, claustrophobic atmosphere with an uncertain future and even more uncertain fellow survivors. At the end of volume one, the outcast makes the girls fight each other to the death for food, for instance, and the girls are hungry enough to agree to it. It can get pretty intense, but also does a good job of feeling realistic and staying somewhat grounded in reality. But I disliked the "bully" themes that were suggested in the summary on the book, as the outcast girl wasn't obviously bullied in the sections of the story that we were shown in volume one. The logic behind the girls being stranded also bothered me, but a plot that resembles Lord of the Flies can't be a bad thing. Suenobu has another series translated into English, Life, that's something like a soapy high school life story, so I think she often works with the themes of relationships between teenage girls. Limit is a good example of the disaster genre though, and volume 4 was released a couple weeks ago.
Drifting Classroom - Kazuo Umezu (11 volumes)
Kazuo Umezu is to horror manga as Osamu Tezuka is to manga in general. An early pioneer, Umezu specializes in creepy, atmospheric stories that frequently feature children turning into monsters, or dealing with an anthropomorphic horror. We do have several examples of his work in English, but his best work available here by far is Drifting Classroom. One day, an entire elementary school is transported to a desert wasteland for an unspecified reason. Leaving the school grounds results in one child falling over dead. Panic overcomes the building, and even the teachers succumb to melancholy and bizarre behavior. Most of the adults are eliminated quickly, save for a lunch delivery man who goes insane and periodically menaces the children through several volumes. The trials in this series are truly incoherent nightmare fuel. The school is periodically invaded by things like floods, or scorpions that eat children. At one point, to stave off some sort of predator, every child in the school pretends to be a piece of furniture so that the creature can't smell their fear. Another story arc starts when the youngest children in the school begin leaping to their deaths from the top of the building. In the real world, the school has vanished, and the parents are in a panic. Somehow the main character, Sho, can communicate with his mom, sometimes by telephone. She periodically does things like bury knives in the walls of buildings, so that Sho can somehow recover them where he is and use them to kill monsters. Things are never really explained. At one point, it's suggested that one of the children planted dynamite underneath the school, and that's how they were blasted into their current predicament. Later in the series, the children realize that the kid that dropped over dead from leaving the school grounds died of a heart attack, so they explore the surrounding area at their will. Westworld somehow shows up nearby, full of robotic horrors. Later, Sho gets appendicitis, and the other grade schoolers operate successfully on him. It doesn't ever try to make sense, it's just bizarre scare after bizarre scare, and lots of screaming grade school children. It was so nonsensical that I found it to be comical, but it was a compelling page-turner because you really needed to know how it was going to out-crazy itself. And it doesn't disappoint. This is a much stranger, more incoherent disaster, but it works so well as an example of the genre, and I am ridiculously fond of it. It finished its English run in 2008, but it either did so poorly it has still not sold out of its original print run, or did extremely well and was reprinted, because all volumes are still available.