Elder Scrolls III. Morrowind.
Keitaro = Nerevarine
Naru, Kitsune, Motoko, Kaolla, Shinobu, Sarah, and Mutsumi = the seven Ash Vampires
Seta = Dagoth Ur
Only problem there would be Keitaro wouldn't meet any of the other members of the Love Hina cast until the very end. Unless you had Tama-chan as Creeper...
Also, Meta, they did a Saiyuki play in Love Hina. Keitaro was Sanzou and Naru was Son Goku (until the end when Naru switched roles with Keitaro so she could be abducted by Seta, who was playing Gyumaoh). Motoko played Gojou, Su played Hakkai Cho, and Shinobu played Sakyamuni. Kitsune played "the chief's daughter", then tacked on another role as Gyokumen Koushu alongside Haruka as Rasetsunyo, while Sarah and Tama-chan had roles as "Kougaiji A" and "Kougaiji B". Even Haitani and Shirai had roles as Kinkaku and Ginkaku respectively. Mutsumi was not present.
God damn was that hard to copy all down.