Sky Fall: Keshitsuku senu Natsu no Hikari

During a school excursion to the Hiroshima Peace Memorial Museum, loner Minami becomes separated from his group. He wanders into a small room with a white door, only to find a strange girl called Sawako getting changed. In his embarrassment, he shuts the door - and finds himself in central Hiroshima, on the morning of August 6th, 1945. As panic sets in, he manages to grab Sawako and her bike and takes the two of them as far from the epicentre as he can, the pair falling into a river as the bomb goes off. They survive the initial blast, but as the immediate effects of the bombing come to light, Minami finds his own memories of the Tohoku Earthquake overlapping with the terrifying reality set out before him...