The ending of a film doesn't need a plot twist or a gruesome act of violence to be surprising (although films that end with gruesomely violent plot twists tend to be my kind of alright). Like losing track of the time only to see the sunrise when you thought it was barely midnight, sometimes the most natural things in the world can catch you off-guard and knock you flat on your ass. some endings - such as that of The Usual Suspects - provide new information that redefines the entire film, whereas the final moments of Tokyo Sonata don't reveal anything so much as they clarify and cohere, collecting divergent strands and themes together in a knot that refuses to be unraveled. Some films leave you with a punch in the gut - Tokyo Sonata ends by finally allowing you to exhale. It's not perfect, but things this beautiful rarely are.
It's an ending that can't really be spoiled in the traditional sense, and one that can be enjoyed even without the benefit of context. Having said that, this is where I recommend that all ye who haven't seen Tokyo Sonata abandon this post and go see Tokyo Sonata. Call me - we can even watch it together. I'll be the guy sitting next to you going "Dude, the end of this movie is soooo awesome" every five minutes. It'll be great. SPOILER ALERT NOW IN FULL EFFECT.