Gekijôban XXXHolic Manatsu no yoru no yume

Beautiful movie and awesome series.

I agree that you need to know the basics of the story to get most of the character interactions.

Yuuko San is a powerful sorceress who grants all wishes but for a price equal to that of the wish. She LOVES sake and snacks and sends Watanuki to buy and make them all the time, much to his annoyance. She's quite funny and mysterious. She sometimes sends Watanuki as bait =) for the spirits when she has a job but she always helps him and asks Domeki to help him.

Watanuki is a highschooler who sees ghosts and spirits that bother him all the time. Yuuko helped him stop seeing these spirits and helped them to not see him either. His price for this wish is to work for Yuuko San as a butler/cook/housecleaner and she sends him to help her with spirits.

Domeki is a fellow highschooler of Watanuki's who is as cool as Watanuki is excitable. Domeki has holy powers that keep ghosts away and his family owns a temple (?). He only likes Hinamori as a friend at most but Watanuki gets jealous whenever then have any interactions.

Hinamori is another highschooler (they all go to the same school) and she doesn't seem to favor either boy but Watanumi has an enormous crush on her. Yuuko San seems to think that there is something fishy about her but it hasn't been revealed yet.

I would definitely recommend this series. The animation is beautiful and the story is very interesting and dark and funny. If you can find it (it is still available on certain sites) check it out.