Ys IX: Monstrum Nox was originally teased as "Project N.O.X." prior to its official reveal. Toshihiro Kondo, president of Nihon Falcom, wanted the next Ys game to lean more towards the adventure genre, similar to the sections of Ys VIII: Lacrimosa of Dana where the player plays as Dana. He also mentioned that he wanted to take the new axis of direction/movement introduced in Ys VIII to the next level (i.e. an air dash or a hook shot).