Amapani!

Their precious magic item was stolen by someone.
They split up to search for them, only to have them all intercepted by the first one they found...
Thus began an adventure in which each of them cooperated with the other while subtly pulling each other down.

Amapani! the name is short for Alice, MArisa, PAtchouli and NItori, is a 2D action platformer developed by Desunoya where up to four players are able to play simultaneously on screen.
While it is possible to play alone, the game also supports online features.
The basic gameplay premise is very similar to Super Mario series, however, Amapani! involves cooperation between four characters with different abilities in solving light puzzles, defeat enemies, open platforms, reach the exit and boss battle at the end of each stage. The game also includes extra stages with greater challenges and harder difficulties.