|This article is about a/an ally in Kaizoku Sentai Gokaiger.|
Cain (カイン, Kain) is an old friend of Luka's.
Luka encountered what appeared to be Cain when he bribed the Sugormin leave her alone. He claimed he had accumulated a large fortune and now the time has come for them to make her dream come true. However, the entire event was staged as "Cain" was actually Action Commander Vannain, using his power to assume Luka's form while keeping her captive along with the real Cain.
Arriving to the Gokai Galleon as the crew were talking if Luka would accept Cain's proposal and leave them, "Luka" arrived on the ship during dinner. Once the crew was asleep, Vannine made his move in setting up explosive charges before leaving ship to detonate them. Meanwhile, Luka and Cain reminisced about how the former made a promise to collect enough money enough to buy an entire planet for them and the homeless children across the galaxy who had been displaced by the Zangyack Empire to live on.
Luka explained to Cain that when she joined the Gokai Galleon's crew, her dream had become even bigger than before as she saw something like Greatest Treasure in the Universe, if as valuable as legends say, would allow her to buy an entire universe with it. Soon after, Vannine returned to announce that he blew the Gokai Galleon up and now intended to kill Luka off. But just as he was about to dispose of Luka, the other Gokaigers arrived to rescue her. They explained that they easily discovered that Vannine was an imposter (he ate broccoli voraciously while as Luka, which is a food that the real Luka detests) and after deactivating the bombs he planted, had Fūraimaru use his illusion technique to stage their ship's explosion to deceive him and follow him to Luka. Enraged that he was tricked as Luka was freed, the Gokaigers fought Vannine.
During the fight, as the Gormin held the others off, GokaiYellow fights Vannine as the Action Commander assumed her form. After Vannine took on Gokai Silver's form, the Gokaigers used the Megaranger Keys to expose the imposter before they use the Gokai Galleon Buster to finish him off. After Vannine was enlarged, GokaiOh and GoZyuJin had a hard time fighting the Action Commander when he assumes the form of a building to sneak attack them.
However, catching on with their heat sensors, GoZyuJin crippled Vannine before Hurricane GokaiOh destroyed him with the Shushutto Shuriken Chain. Soon after, still wanting to make her dream a reality, Cain bids farewell to Luka while claiming that the happiness she obtained while staying with her fellow pirates was a treasure no money could buy.