Sparkling Generation Vakyrie Yuuki is a parody of Japanese mahou shojo (magical girl) comics and anime. The mahou shojo genre features young girls given magical powers to fight various bad guys. There may or may not be some kind of mascot involved and the general theme involves romance, adventure and positive themes like good self-esteem and friendship. Mahou shojo is a genre with a lot of parodies, and deconstructions. Some of these parodies are more than a little racy, and SGVY is one of them.
Our hero (yes, hero) is a young man named Yuuki who really, really loves mahou shojo anime. When he gets his hands on a new anime it turns out to be a magical trap of sorts. Hermod, a Norse god has been tasked with finding a new Valkyrie and decided the best way to recruit a new Valkyrie would be via an anime DVD. Yuuki suddenly finds he’s been turned into a girl and more specifically, a mahou shojo tasked with fighting various monsters and eventually destined to go up against the fire giant Surtr. Yuuki is understandably upset about this transformation, but there is very little he can do about it except survive the attacks of various monsters and the presence of the Norse gods, some of whom are really unhappy with his being a Valkyrie.
The current story arc involves Freya sending former Valkyries after Yuuki because she does not approve of a guy being a Valkyrie. Yuuki would be onboard with no longer being a Valkyrie except the only way he can get out of it is by dying. Meanwhile, Loki is definitely Up to Something involving Freya.
SGVY is an adult web comic with a lot of goofy gag-type humor that tends toward the adult. The art is very reminiscent of a shojo manga. It has a very erratic update schedule though there are usually several pages in the update. Since this manga was started in 2002, there is a very large archive that will probably take a few days to get through. Given the erratic updates, this web comic is best read in archival mode.