User blog comment:KodachiZero/Chain Chronicle V3 on the Wiki + Q&A/@comment-198.51.130.196-20161213233855/@comment-26432452-20161214010409

You mean the v3 taverns? Just finish the certain part of the main story for the respective tavern.

Tap the book icon on the right to see your progress and finish the story quest until you reach the story part with tavern symbol on it. Finish that quest and usually there will be a dialoge box that says tavern unlocked. After that just go to the tavern place on map and tap the red tavern symbol on lower left to open it.