Source: Wikipedia, "Ephemeral Fantasia", available under the CC-BY-SA License.
Ephemeral Fantasia is similar to The Legend of Zelda: Majora's Mask in that the story transpires over a constantly looping period of five days. This is caused by a time loop created by the main antagonist, Xelpherpolis. In order for the time loop to be halted, Mouse must travel through the same five days multiple times.
This game follows Mouse, who has appeared in other games previously with the characters Pattimo, Beak and Fang. Xelpherpolis invites Mouse to play at his wedding, no doubt because of the fame he has acquired on his travels in previous adventures. Of course, Xelpherpolis doesn't expect him to solve the mystery of the island and free its inhabitants.