Manga by author Nishio Ishin - Status ongoing

Koyomi Araragi, a third year high school student who is almost human again after briefly becoming a vampire. One day, a classmate named Hitagi Senjougahara, who infamously never talks to anyone, falls down the stairs into Koyomi's arms. He discovers that Hitagi weighs next to nothing, in defiance of physics. Despite being threatened by her, Koyomi offers his help, and introduces her to Meme Oshino, a middle-aged homeless man who helped him stop being a vampire.

From MangaHelpers:Okitegami Kyouko is a famous detective who solves cases in a single day. In fact, she has to, since her memories only last for one day before they 'reset.' However, for important things, she writes messages for herself down on her body with a special pen. One of her common clients is Kakushidate Yakusuke, a man who is often wrongly suspected of committing crimes. There is also a live-action drama adaptation of this story. [tethysdust]----------------------------The original novel's story is about a detective named Kyko Okitegami who is also known as the forgetful detective. She forgets everything in a day, but solves cases the same day. (Her name has the Japanese word for "today" in it.) An unlucky young man named Yakusuke Kakushidate somehow ends up as the suspect in every case, and he always asks for the detective. [ANN]

Koyomi Araragi, a third-year high school student, manages to survive a vampire attack with the help of Meme Oshino, a strange man residing in an abandoned building. Though being saved from vampirism and now a human again, several side effects such as superhuman healing abilities and enhanced vision still remain. Regardless, Araragi tries to live the life of a normal student, with the help of his friend and the class president, Tsubasa Hanekawa. When fellow classmate Hitagi Senjougahara falls down the stairs and is caught by Araragi, the boy realizes that the girl is unnaturally weightless. Despite Senjougaharaprotests, Araragi insists he help her, deciding to enlist the aid of Oshino, the very man who had once helped him with his own predicament. Through several tales involving demons and gods, Bakemonogatari follows Araragi as he attempts to help those who suffer from supernatural maladies.