Next month, Nintendo will give Switch Online subscribers the chance to purchase Sega Genesis games as part of a DLC pack with N64 titles. And to make the experience as authentic as possible while playing them, the gaming giant is also selling wireless N64 and Genesis controllers exclusively to Switch Online subscribers. The gaming giant showed off a three-button Genesis controller at its most recent Direct stream in the west. Based on a tweet by Nintendo Japan, though, it will release a six-button version in its home country instead.
— 任天堂株式会社 (@Nintendo) September 23, 2021
Nintendo has confirmed to Polygon that the six-button Genesis controller will be exclusively available in Japan. A Nintendo of America rep told the publication that "different regions make different decisions based on a variety of factors" and that the three-button model was the more widely used and more well-known version in the US and Canada. As the publication notes, the three-button model came first, and the one with six buttons was only released when fighting games boomed in popularity. Playing titles like Street Fighter was easier with more buttons to mash. Take note that the Sega Genesis Mini also launched with a three-button controller outside Japan in 2019, whereas the Japanese version came with a six-button model.
Even if you find a way to import the Japan-only controller, it may be better to wait until other gamers have confirmed that it works with consoles in your region. Nintendo doesn't have a release date for the three-button model yet, but it will set you back $50 when it becomes available.