It's pretty much Mario Party Advance but with Danganronpa characters.
Go around a board, pick up stats to make your character better and eventually beat a boss to unlock the next island. You can tell it was a side mode previously because of how basic it is and the lack of any new voice acting but the gameplay loop is pretty fun...... it just lacks a compelling reason to keep coming back. Like the events are nice, it's cool seeing the different casts of characters interact but it's not enough to put a lot of time into.

The most annoying thing is that outside of the initial starting cast of protagonists, everyone else is unlocked through grinding for coins for a gacha machine and that is awful. Like a random chance to get a character I want to play with? Nah, not fun and the fact you can pay real money as well for this as well makes it even worse.

Ultimately this is a cheap cash in on the anniversary that works as a nice bonus game for buying the trilogy on Switch otherwise it isn't worth checking out on its own