This is a sort of cameo / appearance double item. In the game Monster Hunter 4 Ultimate, you could meet "Felyne" which is a cat type helper animal thing. As a sort of bonus content in 4, you can dress up your Felyne with this Sonic costume. It has gloves, shoes, spikes & a blue suit. Instead of the regular belly dot though, it is a cartoon paw-print. Notice the regular felyne arms (striped) as the suit has no sleeves.
But that's not all! You can also arm it with Caliburn, Sonic's sword from Sonic & Black Knight game. (Monster Hunter games use a lot of weapons /swords so having the special sword as a cameo item as well makes sense. This is a fun extra!