The game builds on the first one with some major changes. Most noted, a crafting/upgrade system.
The crafting/upgrade takes a bit of experimenting with to understand the gear stats. All equipment has a maximum upgrade level.
Another change is a new type of equipment. "Backpack" equipment. These can range from acting as a shield, providing healing, attacking a single enemy, or attacking all enemies. Many more options and strategies with these.
It does take time to understand what's going on with the menus. Don't be afraid to pick up the app because it's in Japanese! It's a fun game. :)