Eu esperaria que a maioria dos países permitisse exceções aos seus procedimentos habituais de imigração em casos de emergência (pode até haver algumas leis internacionais sobre isso). O Japão, no Artigo 17 da Lei de Controle de Imigração e Reconhecimento de Refugiados :
In the case of disease or any other accident which urgently requires the landing of a foreign national aboard a vessel or aircraft for the purpose of medical treatment, an immigration inspector may grant permission for emergency landing to the foreign national concerned based on an application by the captain of the vessel or aircraft or the carrier who operates the vessel or aircraft until the cause thereof ceases to exist, subject to a medical examination by a physician designated by the Minister of Health, Labour and Welfare or the Minister of Justice.
(Note que no jargão da imigração japonesa, pouso significa entrar no Japão passando pela imigração, etc.)