Title: Ranma ½: Kessen Tougenkyou! Hanayome wo Torimodose!
English title: Ranma ½: Nihao My Concubine

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)