Tokuma Shoten
"Grave of the Fireflies" is the first Studio Ghibli film that Disney never had distribution rights to in North America, since the film was not produced by then-parent company Tokuma Shoten (Disney formerly handled the North American distribution of all Tokuma Shoten-produced Studio Ghibli films before GKids picked up the distribution rights.) but by Shinchosha, the publisher of the original short story (as mentioned; although Disney has the Japanese distribution rights themselves).