The Japanese title of this episode is "Chou-musabetsu kessen! Ranma team vs densetsu no Houou."
This is an oav.
Originally released with "Oh, Cursed Tunnel of Lost Love! Let My Love Be Forever" on the tape entitled "One Grew Over The Kuno's Nest"
While sold as part of the OAV series in the US, it is actually the third Ranma movie, released theatrically together with two other unrelated short films in Japan.