If you liked the xxxHolic manga, the Anime-Planet community thinks you'd like:
Shirihama Kenichi is a weak scaredy-cat, and his status as the karate club's punching bag has earned him the name of ‘Weak Legs'. One day Kenichi meets Miu and, impressed by her skill after she effortlessly throws him to the ground, he follows her to the Ryouzanpaku dojo. There he finds five great masters of martial arts, and driven by his desire to become stronger, he begs them to accept him as their student - though it won't be easy. Kenichi endures harsh training (and injury) from Akisame - the philosophizing Jujitsu master; Apachai - the Muay Thai ‘God of Death'; Kensei - the ecchi Chinese Kempo Master; and Shigure - the weapons prodigy. Finally after proving his determination, he is accepted by Shio - the 100-dan Karate Master, who had initially wanted nothing to do with him. Now Kenichi walks the long and arduous path to becoming a master himself, all whilst trying to protect those he cares about from anyone who would dare to harm them.
Over eighty years ago, a great war raged over the natural resources of the planet. To assist in the battle, the bodies of fallen soldiers were recycled - with a stone heart made of a limitless power source, these ‘Undying' fought in the war, only to be hunted down after its end by the Church. Now, in the present, Kieli is an orphan who has had the ability to see ghosts, keeping her an outcast from her peers. However, when she and a ghost friend meet a strange boy named Harvey, Kieli discovers that she's not the only one who can see spirits. Curious and excited, Kieli now travels with both Harvey and Corporal, a spirit possessing a radio, on a quest to lay Corporal's soul to rest. Along the way she'll experience danger and touching moments, as well as inadvertently helping ghosts find their peace.
Both Kieli and xxxHolic contain a weird mix of the supernatural and humor. It's hard to describe, because so few series mix spirits, violence, and comedy! If you enjoyed one of these, the other should catch your interest as well. :)
Kazahaya Kudo and Rikuo Himura are two teenagers who work for the ‘Green Drug Store,' and also rent an apartment above the store. Rikuou rescued Kazahaya from freezing to death on the streets during the winter, and although Kazahaya is grateful to Rikuo for this, the two can't seem to get along. The mysterious Kakei owns the store and Kazahaya often has to put up with the constant teasing of Kakei's friend Saiga. The strangest thing about Kazahaya's job is that he and Rikuo are often sent on "extra jobs" by Kakei, which are different and more bizarre each time. But because he needs the money to avoid ending up on the streets again, Kazahaya never refuses any job offered to him no matter what strange situation he may find himself in. Just what secrets do each of these four men hide, and why is Kazahaya so reluctant to return home?
As in other Clamp works, xxxHolic does cross over into Legal Drug more prominantly, though there are plenty references to other Clamp works such as Tsubasa, Chobits, and CCS. Moreover, the characters of Domeki Shizuka and Watanuki Kimihiro are so very similar to Kudo Kazahaya and Himura Rikuo,(same template but with a more shounen-ai twist within Legal Drug) as they form this duo of supernatural guardian and medium roles. There are tiny variations between both, such as a seemingly innocuous pharmacy run by a man enshrouded by mystery (Kakei and his pharmacy) versus a wish-granting shop run by a witch enshourded by mystery (Yukko and her shop). Both deal with supernatural dangers or tasks that must be completed by the duo, though each series has its own drama and depth.
The male leads in Let's Fight Ghost and xxxHolic have a similar ghost problem, but they way with dealing with it is vastly different. If you find the "guy sees ghosts" theme interesting, you should give both of those a try.
P.S. Let's Fight Ghost gets strong on tragedy and drama later on which in turn makes those two series more similar.
In feudal Japan, evil spirits known as mononoke plague both households and the countryside, leaving a trail of fear in their wake. One mysterious person has the power to slay the mononoke where they stand; he is known only as the Medicine Seller, and he vanquishes the mononoke using the power of his Exorcism Sword. However, in order to draw his sword he must first understand the Form, Truth and Reason of the mononoke. Armed with a sharp wit and keen intellect, the Medicine Seller wanders from place to place, striking down the mononoke in his wake.
Though xxxHolic has far more comedy, both these manga focus on the world of the supernatural and the effect that spirits and youkai have on the human world. While Mononoke focuses more on human folly, and xxxHolic on fate, it may be worth your while checking out one if you liked the other.