Basically, they both wanted to do it, how boring
I’m still surprisedHyrule Warriorsexists and it’s not because of thegratuitous cleavage. My favoriteZeldadirector, Eiji Aonuma, is apparently supervisor on the Tecmo project, which is being produced by Hisashi Koinuma and Yosuke Hayashi. They talked with Famitsu, as translated here bySiliconera, about how the collaboration happened.
“Warriorshas teamed up with series such asGundam,Fist of the North StarandOne Piece, and I thought about doing something with Nintendo,” explains Koinuma. “While thinking about what would make for a good collaboration, it was Hayashi that proposed [the idea] by saying, ‘Wouldn’t it be interesting to do a collaboration withThe Legend of Zelda?'”

They spoke with Eiji Aonuma and Shigeru Miyamoto, whom agreed on the collaboration. Aonuma apparently considered the idea of a cross over years ago when Tecmo announced theOne Piecegame. “Miyamoto told me, ‘The folks at Tecmo Koei are talking about aZelda Musou. Are you interested?'” Aonuma said, “and I responded with ‘definitely!'”
“You can say that luck also played a role,” Koinuma said. “The title that our company wanted to do aMusougame collaboration with the most just so happened to be the one title that the folks at Nintendo said ‘we can entrust them with this one’ to, so we were both able to come to an agreement regardingThe Legend of Zelda.”

There you have it. Still weird. I wonder if this will lead to moreWarriors/Nintendo cross-overs. I mean, not like Nintendo is interested in makingStar Foxgames itself.
Nintendo And Tecmo Koei Discuss How Hyrule Warriors Came To Be[Siliconera]







