The main character is a detective, Kazuhiko Amamiya, suffering from Multiple Personality Disorder (a.k.a. Dissociative Identity Disorder). Starting out as a violent detective series with a twist (the twist being the variant personalities that take over Detective Amamiya at various intervals), the series evolves into an exceptionally complex and involved sci-fi conspiracy story.

From CMX:

MADARA tells the story of an apprentice blacksmith in a rural village who gets by using artificial limbs created by his adoptive father. But when a chance encounter with the demon Moki reveals Madara's true destiny, he's catapulted into a mythic quest! His real father, the evil despot Miroku, feared long ago that Madara was destined to kill him and rule in his place. After Madara was born with tremendous powers, his body was cut up, and the parts divided amongst eight evil generals. Now Madara, with the help of a band of freedom fighters and a magical sword, sets out to retrieve his body parts and defeat his brothers, who covet the throne. As he fights his way across the world, he contemplates the prophecy: How will he wrest control of the kingdom from his father and win the people their freedom?

On the seventeenth birthday, a virgin must be sacrificed. But why?

After a long absence, the young shaman Samizo Kohei returns from the dead with a prophecy of the apocalypse. Or part of him returns, at least - most of his body has been replaced with the transplanted body parts of his former friends, all retaining their distinctive personalities. He returns to his home in Shinjuku, where he works as a psychic surgeon in an unlicensed clinic. Here he serves as the unofficial guardian of the Shinjuku underground, solving paranormal murder mysteries, with the assistance of an assortment of other bizarre mystics and semi-human allies. Meanwhile, the others wonder exactly what Kohei has become, and whether he has returned to prevent the apocalypse, or to initiate it.

Meet the extended staff of JDC, quite possibly the oddest detective agency ever formed, which includes a strange boy with a circle tattooed around one eye, a man missing his mouth, another man in a ball-gag, a woman in a cartoon mask, a socialite… and yet they all come together to solve murders that ordinary police cannot seem to grasp, and there’s a reason for that…

Two brothers, Shunpei and Kyouhei, have very opposite characters but share a crush on their cute sister Anko. The three of them live with their excentric father, may (or may not) have diffferent mothers, have fun, lots of tantrums and try to lead a happy life in junior high school.

From Omanga:

Eiji Otsuka and Sho-u Tajima at it again, Eiji in a much more minor role this time, however. In any case, this a relatively older and short comedy series (4 volumes) that should be a fun break from their usual mayhem with MPD (Multiple Personality/Dissociative Identity Disorder) .

In 1994, this manga was published as a whole under title "BROTHERS High School".

Side story/prequel to "The Kurosagi Corpse Delivery Service."Matsuoka Kunio is a writer and anthropologist, but he's much more interested in playing detective. Joined by his long-suffering best friend, a very unorthodox priest, and a boy with the power to raise the dead, he investigates the occult mysteries and murders of early 1900s Japan.