Multiple playable characters and a potential 3DS first
http://www.nintendoworldreport.com/news/42288/new-details-emerge-for-zero-time-dilemma
Last week's edition of Famitsu contained new details about the upcoming Zero Time Dilemma in the game's first acknowledgement in Japan.
The article confirms that Zero Time Dilemma will feature three playable characters, with probable switching between different teams where you control the leaders. There will be five new characters in addition to returning cast members from the previous two Zero Escape games.
Although not confirmed, the article discusses the possibility of a CERO Z rating for the game in Japan; should this happen, it would be the first 3DS game to reach the rating. Zero Time Dilemma is expected this summer, and new details will emerge this week as director Kotaro Uchikoshi is in San Francisco for the 2016 Game Developer's Conference and a trailer will run on the game's website on March 17.
What is a CERO Z rating?
CERO is the rating board in Japan. "A" is for All Ages, "B" is for ages 12 and up, "C" is for ages 15 and up, "D" is for ages 17 and up, "Z" is for ages 18 and up.
While 18+ is obviously adult only, I wouldn't equate it to the esrb adult only. AO esrb games would be something intensely violent like uncensored Man Hunt 2 or something erotic in nature, whereas I'd say Cero Z is more like a slightly harder M in the same way you have Pegi 16 and 18.