Nintendo just suddenly uploaded this teaser this morning to all their YouTube channels and social media pages, accompanied by a hashtag going "WhoIsEmio." The only confirmed details in the trailer is that it is in fact a Nintendo first party game as it ends on their logo, is coming to Switch as it starts on its logo, and it's rated M for mature as can be seen in the corner of the North American version of the teaser. The Japanese that appears translates to "The Smiling Man" according to others.
My two biggest guesses on what Nintendo's teasing:
1. Nintendo's first new horror IP in over two decades (last one was Eternal Darkness on the Gamecube), with the "Smiling Man" being a paranormal entity.
2. A psychological detective thriller about catching a serial killer called the "Smiling Man."
Either way I'm certainly interested, this came out of nowhere and if it is indeed a horror game then it'll be quite intriguing to see Nintendo dip back in to the genre again 22 years after Eternal Darkness.