A fairy who takes over a girl's body... The treasure hunter Barrett, while drowning in carnal male pleasure, has his wish to have his body turned into that of a woman granted by the girl. Barrett, with his new body, becomes the girl's Chevalier: a fighting maid.

What anime would you recommend to me if I'm into horror/mystery anime?

Horor eh? I’ve got it. Mermaid Forest According to an ancient Japanese legend, mermaid flesh may grant immortality if eaten.
However, there is a much greater chance that consumption will lead to death or transformation into a damned creature known as a Lost Soul (or Deformed Ones in the English dub).
Mermaid Saga tells the tale of Yuta, an immortal who has been alive for five hundred years.
Throughout the series, he wanders across Japan searching for a cure and meets others whose lives have also been ruined by mermaid flesh. Majin Tantei Nougami Neuro The series follows Neuro Nōgami, a demon who depends on mysteries for sustenance.
Having consumed all the mysteries in the demon world, Neuro travels to the human world in search of more.
There, Neuro recruits high school student Yako Katsuragi as a facade for a detective agency. Ghost Hunt It follows the adventures of Shibuya Psychic Research as they investigate mysterious occurrences all over Japan with a team of other spiritualists and clever assistants. Shinrei Tantei Yakumo Haruka Ozawa's sophomore year is getting seriously scary.
One of her friends is possessed, another has committed suicide and Haruka could be the next one to flunk the still-breathing test.
Her only way out of this potentially lethal dead end? Yakumo Saito, an enigmatic student born with a mysterious red eye that allows him to see and communicate with the dead.
But the deceased don't always desist and some killers are more than ready to kill again to keep dead men from telling any more tales.
That doesn't stop Haruka's knack for digging up buried secrets, and there's even more evidence of bodies being exhumed by both Yakumo's police contact and an investigative journalist with a newly made corpse in her closet! Watch to know more. Ghost stories Kids and ghosts.
When young Satsuki finds an old book of spells from her passed away mother, she gains the power to fight ghosts that are haunting her new school.
With the help of her friends, and of a really wicked devil cat, she must protect everyone around her or be haunted for ever more. Yup.
Thats it.
Have a sweet nightmare.
:) Edit: For the anime Ghost Stories, I recommend to watch the dub because it is more humorous and funny.