Well we didn't have to wait to long to learn more about what that Nintendo tease trailer was as a new page has popped up on the Nintendo store showing us more along with a new extended trailer. And it's not that far off!
Emio The Smiling Man: Famicom Detective Club has been officially unveiled by Nintendo. Set to arrive August 29th 2024 it will be the third game in the Famicom franchise and first in 30 years.

As per the Nintendo store listing the game we learn a bit about what we will be doing in the latest instalment:
"A student has been found dead! His head was covered with a paper bag with an eerie smiling face drawn on it"”much like the victims of Emio, the Smiling Man"”a killer of urban legend who is said to place such a bag over his victims' heads.
As an assistant private investigator, you are tasked with helping police solve this crime, which is reminiscent of a series of unsolved murders from 18 years ago. Has a serial killer returned, or is this the work of a copycat? Are these crimes inspired by the Smiling Man story, or the origin of it?"
Emio The Smiling Man is certainly a departure from Nintendo's more family friendly games. It will be very interesting to see how it's received amongst the fanbase in August. The trailer is she restricted but you can watch it here.