Ys vs. Trails in the Sky: Alternative Saga[a] is a 2010 crossover fighting game by Nihon Falcom.

[1][2] It takes its roster from two of Nihon Falcom's series, Ys and Trails, and is played from a top-down perspective.

[6][7] From Ys, there is Adol Christin,[8] Dogi,[8] Elk, Mishera, Aisha,[8] Geis,[8] Cruxie, and Chester Stoddart.

[9] From Trails, there is Estelle Bright,[6] Joshua Astray,[6] Tita Russell,[8] Agate Crosner,[8] Olivier Lenheim,[8] Kloe Rinz,[10] Renne, Leonhardt, and Lloyd Bannings.

[4] The game was created due to Nihon Falcom's desire to make use of the PlayStation Portable's wireless ad hoc local multiplayer function, something they had not been able to work into prior JRPG titles.