Ranma ½: Kessen Tougenkyou! Hanayomewo Torimodose!

らんま1/2 決戦桃幻郷! 花嫁を奪りもどせ!!

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: Anime News Network)