It has been long rumored that Kingdom Hearts 3, the famous Japanese action RPG game created by Tetsuya Nomura, will include "Star Wars" and more "Disney" characters.

And finally, Tai Yasue, the game's co-director and designer talks about the details of the upcoming Disney and Square-Enix crossover that includes "Star Wars" and "Marvel" cast in his interview with Kotaku.

"Yeah, I can't go into specifics, but there's a LOT of new Disney stuff and we have our plates full," Yasue explained. "Theres a lot to consider - we're looking at all of Disney, the new ones as well, they have a lot of pull and draw.

"We have to come up with a world that has a lot of originality. We want variety in our new Kingdom Hearts, so we don't want too many of one sort of world that would look the same. For each world there has to be some meaning for it, in the plot; in Birth By Sleep, for instance, in the Cinderella scene, the characters learn something specific by relating to Cinderella. Also, gameplay-wise, is that world something that would make gameplay fun? There's a lot I can't say, but there's so much to consider."

While, he did not go into specifics about what Disney characters would be included in the upcoming "Kingdom Hearts 3" game, he did mention that "Star Wars" and "Marvel" are taken into consideration.

"Well, yeah. They're all under consideration," he admitted. "Nothing's off-limits, we're considering all of the worlds. There are so many wonderful concepts. We're happy about that, but at the same time it's really tough to choose."

Meanwhile, Yasue further explained the team's decision from switching to their in-house engine Luminous to Epic's Unreal Engine 4 half way through the development of Kingdom Hearts 3 upon talking to Euro Gamer.

"The technology is moving forward a lot," he explained. "That's something we've learned from the West, I think, in a big way. We're using Unreal Engine 4 right now, and that really has changed the way we make the game."

And when asked if something went wrong with Luminous engine while in the development of Kingdom Hearts 3, Yasue said:

"There was nothing wrong with the Luminous engine at all," Yasue assured. "We decided that Unreal 4 was right for us. There was a huge network of people actually using it, we were communicating with the Japanese people at Epic a lot - it was like a complete product.

"It was easy to shift to, but at the same time though, there was a lot of stuff specific to Kingdom Hearts that we couldn't really do on Unreal 4 at first. So we had a lot of co-operation from Epic - they did a lot - at the same time we were doing a lot of customization of the engine as well, to suit our needs."

The game designer also explained the process of the customization, which the team referred to as Kingdom Shader, the paintbrush-like aesthetic of Kingdom Hearts 3.

"A lot of painstaking detail - the shadows for example, the really vivid colours, that sort of thing - we couldn't really do at the beginning, so we had to remake/customize the engine and add a lot of parameters."

Yasue also cleared speculations of completely scrapping the teaser trailer that was shown during E3 2013.

"We use the same graphical assets, so we didn't throw any of that away, and I guess a lot of the experience we got from making that for E3, that experience really translated to our development now," Yasue explained.

Watch the teaser of Kingdom Hearts 3 below:

"It was in our initial production stage, so I think we were learning a lot of stuff while using the Luminous engine."

Are you excited to see "Star Wars" and "Marvel" characters in the upcoming "Kingdom Hearts 3" RPG game? Sound off in the comments section below