Astral Chain, the upcoming Nintendo Switch game from PlatinumGames, has optional local co-op, but it allegedly makes the game more difficult.
Astral Chain’s director Takahisa Taura revealed this information in an interview with Kotaku, saying (via a translator) “You may have noticed that the characters are connected by a chain... when you’re controlling two characters, that chain allows you to see where the other character is in relation to the one that you’re controlling.”
While this mechanic was designed for one person to control two characters at once, the Switch’s inherent inclusion of two Joy-Con inspired Taura to incorporate co-op. “I thought as I was developing the game that, of course, it could be made into that kind of system where it could be split up, but generally what I wanted to do is have one player control two characters at the same time. But the Switch actually has this great feature where, obviously, you can detach the Joy-Con and share play. We wanted to take advantage of that as well.”