The 13th century Japan depicted in “Ghost of Tsushima” never existed, though you’d be excused for thinking it at least reflects a real place. All the motifs of the samurai action genre are present, after all. Lush green fields and bamboo groves sit, improbably, next to snowy mountain ranges and forests of blood-red autumn leaves. A scowling lord in ornate armor talks endlessly of duty and honor to his younger warrior charge, the protagonist Jin Sakai. Even the rough outline of the time period seems to match with a vague awareness that, yes, the Mongol Empire under Kublai Khan did attempt to invade Japan around that time.