Cels Forum

The main difference is in what the young ladies wear when
they go into dominatrix mode.  Tira wears an all-black outfit
instead of that orangish outfit from the television series.
The other girl "wears" suspenders as her only form of upper
torso clothing.  The art is a little  nicer, though the television
show was pretty darn nice.  The story is completely lacking
in the ovas... guess that's getting off topic though.

Oh, and sorry, no clue where to get cels from the ovas.
If I had to try anyone though it would be Anime Link.