Hakuba Keijiro doesn't have any interest in girls, until he meets a beautiful girl that is also very unusual. The girl in question is dressed in an old-fashioned style, and seems to have nearly complete amnesia. The only thing she remembers is that her name is "Hiiragi." Keijiro gets his parents to take guardianship of her while they look for her real family, and Hiiragi moves in. But who is she, really? Is she a princess, come through some kind of time-slip? Is she something supernatural? Hiiragi herself would like to know...

From Viz:

Megumi Amatsuka, a rough and tumble nine-year-old boy, always dreamt of becoming the "manliest man on earth." Upon receiving a book of magic from a sorcerer whom he saved from a group of local thugs, Megumi summons a genie in order to make a wish. But due to a sick twist of fate, the genie turns out to be an evil one, and Megumi winds up being the "womanliest woman on earth"! Six years later...Megumi is the most desirable girl in school, but deep within her hot-mama façade is the same trash-talkin', punk-stompin' boy.

Omaezaki Sanemichi was born into a near-perfect existence. His family is wealthy and powerful, and he's good-natured, smart, and athletic as well! All the girls at his high-school dream of having a Cinderella-style romance with him, and, though they are desperately jealous of him, none of the boys can come up with a legitimate reason to publicly hate him.

But one day the unthinkable happens: Sanemichi's family's flagship company collapses and his father flees. Sanemichi and his former servants, the teenage siblings Natsuno and Asasuzu and the absent-minded old man Furukawa, are left without a dime. Will Sanemichi be able to maintain his gentlemanly behavior despite the humiliation and many hardships that face him?

What would happen if you took a normal Japanese kid, flew him to Nevada, and then raised him on stories of feudal Japan? "I'm Doushirou" would happen. Now Doushirou is back in Japan and is facing the difference between what he's been told all his life and what his own eyes and ears are telling him.

Two boys, Mitsuhashi Takashi and Itou Shinji, meet each other at a salon. It turns out both boys are transferring to a new school and decide to take the opportunity to reinvent themselves. No longer will they be run of the mill high school students, they will become the biggest delinquents Japan has ever seen!

The story follows the high-school delinquent Masaya Funebashi, better known as "Devil Ma-kun" who is trying to reform his image by joining the tea ceremony club.

From MangaHelpers:

Scientists predicted an imminent meteor impact on Earth that would annihilate civilization, but contrary to their prediction, the meteor missed Earth. Though avoiding immediate destruction, humanity found that the meteor left behind something in its wake, something that would change the course of civilization forever: a new form of bacteria that ate through all known metals.
Facing this new era where all metals turn to ash, Jinkichi and his classmates will have to survive with little help from the Japanese government. Some of his classmates have already begun to understand that the norms of the past have collapsed, and lawlessness will be the new law. Jinkichi will have to protect himself as well as his classmates from the violence that ensues.