Ranma ½: The Movie 2 - The Battle of Togenkyo: Rescue the Brides!
A comedy film that brings humor and levity to its premise.
Ranma and the gang are invited to a boating trip with Kuno. Unfortunately, a storm destroys the yacht and everyone is stranded on a remote island. The whole situation goes even more awry when one by one, the girls disappear without a trace. Ranma then finds out that the girls are abducted by Toma, ruler of the island, as part of his personal harem. (Source: ANN)
Plot summary from MyAnimeList. Data and images via Jikan API.