what is the name of a spirit that takes the human form in a very sensual manner

Incubus or succubus?

A siren?

My last girlfriend!

Jack Daniels

If demons are spirits  -and if Pinkfreud thinks they are, they are -
then here is the website for you:

INCUBUS AND SUCCUBUS - 
Incubus and Succubus Keywords: Incubi, Succubi, Incubus, Succubus Preface ...
INCUBUS AND SUCCUBUS: DEMONS THAT HAVE INTERCOURSE WITH YOU. ...
www.jesus-is-lord.com/incubus.htm - 18k -

Considering the name of the site, I was surprised at the all capitals
in the preceding line.  Sounds kind of promising ...

I am pretty sure (again, if demons and more friendly types of mythical
beings count as spirits) the Hindu and Buddhist religions offer some. 
You may have to put up with a few extra arms, but in the pictural and
statuary representations that doesn't seem to impinge or their "very
sensual manner".
But if you want a personal experience, stick with Incubus or Succubus,
probably Incubus for a Liskalynne; those oriental ones prefer the
company of other many-armed types.
Oh, do the hurris in Muslim heaven count:  the virgins promised to men
who die while defending their faith?

The answer is Incubus.....unless the creature has sex, then it would
be the Succubus.
Many answers like this can be found by visiting this new-age site/shop......
www.bell-bookandcandle.net  there are many well informed books on the
subject as well as many other spiritual subjects ! theres something
for every interest o0n this site shop.

Hmmm!  My website says that incubi want to have sex with women and
succubi with men, but maybe Moonhawk has more experience with them
than I do (he can't have less).  Somehow it reminds me of Heinrich
Kleist's  "Die Marquise von O" ...

myoarin is correct