Ishin Nishio

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 (myanimelist.net)

Follows Araragi's encounter with the vampire Kiss-shot Acerola-orion Heart-under-blade and his journey back into humanity from being a vampire. (imdb)

In the spring of his second year of high school, Koyomi Araragi met the beautiful vampire Kiss-shot Acerola-orion Heart-under-blade. Koyomi saved Kiss-shot, who was on the verge of death with all four of her limbs cut off, but only at the expense of becoming her minion and a vampire. "In order to go back to being a human again, you must take back all of Kiss-shot's limbs." After receiving advice from Meme Oshino, an expert in the supernatural, Koyomi prepares to go into battle... (imdb)

With help from Meme Oshino, the apparition specialist, Koyomi defeats the three powerful vampire hunters: Dramaturgy, Episode and Guillotinecutter. Koyomi takes back all the limbs of Kiss-Shot-Acerola-Orion-Heart-Underblade in order to become a human again. But, when he returns to Kiss-Shot, she reveals to him the cold truth of what it means to be a vampire--a creature of the night. Unable to take back what he has done, Koyomi feels nothing but regret and can only deny his dreadful fate... (myanimelist.net)

The morning after his high school graduation ceremony, Araragi goes to the bathroom to wash his face but is struck by the sensation that his reflection is watching him. Touching the mirror, Araragii's hand passes straight through and he is sucked into a mysterious world. (themoviedb)

In each episode, Koyomi is presented with a mystery posed by one of the female characters from the story, which he then investigates on his own or helps them solve.

Mild-mannered Koyomi Araragi sticks his neck out for a dying vampiress and ends up tasked with fetching her missing limbs. (366weirdmovies.com)

After high school, Koyomi Araragi's story ended. However, the stories of the girls he saved continued, serving as prequels or sequels to their youthful struggles.