There are several ways to strengthen your Meowmates in the game currently:
1. Level Up
Use EXP Potions earned from the main story to level up your Meowmates. Keep in mind that an Meowmate’s level cannot exceed the Captain’s level.
2. Star Up
Consume Meowmate Shards to raise the star level of that Meowmate. After reaching ★5, you can continue enhancing them through Transcendent Awakening using the Hearts and Meowmate Shards.
3. Tier-Up
Use materials such as Water Bottles, Compasses, Lanterns, and Maps (all obtainable from the main story) to Tier-Up an Meowmate. The Tier-Up cap increases as the Meowmate's level goes up.