The Pegasus Add-on for Groove Coaster has 6 achievements.
Play Pegasus 20 times
Play Pegasus and clear all of SIMPLE, NORMAL and HARD
Play Pegasus and get A Rank in SIMPLE, NORMAL and HARD
Play Pegasus and get S Rank in SIMPLE, NORMAL and HARD
Play Pegasus and get S+ Rank in SIMPLE, NORMAL and HARD
Play Pegasus and get S++ Rank in SIMPLE, NORMAL and HARD