What would warriors returning to fight their wars in the afterlife look like? In Japan, they are sometimes imagined as fireflies.”Grave of the Fireflies” ties two wars together with visual poetry.

Once upon a time, there was a great civil war in Japan between the Taira and the Minamoto clans. At first the Taira were able to gain the upper hand, and ruled through the emperor in the capital of Kyoto from 1160 to 1185. But in their kindness was born the instrument of their defeat. They did not kill all of the Minamoto and two great leaders rose: Yoritomo and Yoshitsune. Yoritomo organized a revolt against the Taira and under his rule his greatest general Yoshitsune would be forced into exile and finally killed. For the first time the capital of Japan would be moved from Kansai to Kanto, from west to east–not in Tokyo but in nearby Kamakura. The war is known variously as the Genpei War (源平合戦  Genpei Kassen) or the Taira-Minamoto War (also Jishō-Juei War (治承寿永の乱 Jishō-Juei no ran). The Gen is for the Minamoto  (源 Gen) and the hei or pei for the Taira (平 Hei), using the alternative way of reading the kanji.

There’s a Japanese folktale that says the defeated Taira became fireflies and rise each summer during the Obon season for a brief respite. Japanese fireflies only glow in the night for two weeks. Among the species found in Japan, two are named for the Taira and the Minamoto: The Genji 源氏 and the Heike 平家 or the Genjibotaru (Luciola cruciata) and the Heikebotaru (Aquatica lateralis).

• The rest of this essay is available on Amazon: “Monjilla on Movies: Essays on Anime.”