Undertale
A charming, often funny, and always deliciously weird game that at first glance may appear to be a JRPG (as others have noted, most like Mother/EarthBound), but is really more of a free-form improvisation inspired by JRPGs, as well as other thought-provoking indie games of recent years (Braid and Fez come to mind).
It's longer and more varied than you might think, and well-worth playing to the end.
However, be aware that you cannot experience the whole game in the first playthrough. Some call this "replayability." I call it "annoying." However, I promise you that even if you can only commit to one playthrough, you will "get it," have fun, laugh, and be provoked to think more deeply about accountability, responsibility, and morality.
I would also like to thank the developer for supporting Linux.