As you collect more Keychains, you'll gain new ranks on your Save File.

Ranking	How to unlock
Dream Land Bandit	After Collecting 100 Keychains.
Fair-Weather Collector	After Collecting 25 Keychains.
Keychain Hunter	After Collecting 50 Keychains.
Keychain Master	After Collecting 256 Keychains.
Kirby Maniac	After Collecting 150 Keychains.
Legendary Collector	After Collecting 200 Keychains.
Superstar Collector	After Collecting 250 Keychains.