林に千の鳥より、手に七の鳥

There are seven of them. Final achievement is gated behind beating the Deer in the main story.

The phrase is a variation of the popular saying "A Bird in the Hand Is Worth Two in the Bush." The original saying implies that it is better to hold onto something you already have, rather than risk losing it by pursuing something uncertain or potentially greater. The modified version exaggerates the idea of keeping what you already have, suggesting that the value of having a sure thing is far greater than the potential benefits of seeking greater rewards that are uncertain or difficult to obtain.