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Hikari no umi (Hikari sea)
by Sappō Satō
Drawings by Machiko Kumagai
Tōkyō Hōrei Shuppan, 2016, 26 pages

This illustrated book, designed for adults to read to young children, tells the tragic true story of a kaiten human torpedo pilot named Nobuo and his wife Yukiko.

Nobuo and Yukiko grew up in the same town in Hyōgo Prefecture and always played together when they were children. In one conversation together, Nobuo said he wanted to help people when he grew up, and Yukiko said she would like to be his wife. The most memorable time they shared together in childhood was when Nobuo took Yukiko to a secret place where at dusk fireflies lit up the sky.

Nobuo became a university student in Tōkyō, and later he volunteered to join the Navy during the Pacific War. On a visit by Nobuo to his home, he and Yukiko decided to get married even though he did not know if and when he might die. They were married two days before he began his assignment at Hikari Base in Yamaguchi Prefecture. She accompanied him to the base, but she knew nothing about the base's top-secret kaiten weapon, designed based on an existing torpedo in operation and steered by a pilot into an enemy warship.

Several months later, Yukiko received a message asking her to come to Hikari, since he soon would be leaving on a mission. Nobuo and Yukiko sat together on a hill overlooking the sea off Hikari, and they again saw the light of many fireflies as they looked at the sea. The next morning Yukiko went back to the hill and sadly said farewell to Nobuo as his submarine left the harbor at Hikari. One month later he died when launched in a kaiten from his submarine. Yukiko did not receive official notification of his death until a couple of weeks after the war's end on August 15, 1945.

About ten years later, a former American warship captain came to Japan and visited with Yukiko. He commanded the ship that Nobuo tried to hit but missed, so he told Yukiko about Nobuo's last moments. He described the innumerable golden lights around Nobuo's kaiten weapon that he saw deep in the sea. Yukiko thought that these must have been fireflies that guided him to heaven.

Yukiko believed that Nobuo gave his life for his country and for his family who he loved. After having spent less than ten days together as a married couple, Yukiko never remarried and worked many years as a knitting instructor. Her hope is for a peaceful world.

On June 28, 1945, Lieutenant Junior Grade Nobuo Ikebuchi died in a special (suicide) attack at the age of 24 when submarine I-36 launched his kaiten manned torpedo. On June 4, 1945, submarine I-36 made a sortie from Hikari Kaiten Base in Yamaguchi Prefecture with six kaiten pilots who were members of the Kaiten Special Attack Corps Todoroki Unit. Submarine I-36 headed for a patrol off the Mariana Islands. He was from Hyōgo Prefecture, attended Nihon University, and was a member of the 3rd Class of Navy Branch Reserve Students (Heika Yobi Gakusei). He received a promotion to Lieutenant Commander after his death by special attack.

The book is based on the true story of Nobuo and Yukiko Ikebuchi. Although the former American captain's name and ship are not mentioned in the book, sources indicate that this was the USS Antares (AKS-3), since Ikebuchi's attack was on this cargo ship [1]. The Japanese word hikari means light and is also the name of the kaiten base where Ikebuchi was stationed. The light from fireflies plays a key role in three scenes, but it seems that the former captain's description of many lights deep in the sea around Ikebuchi's kaiten probably did not actually occur.

The book's author, Sappō Satō, first met Yukiko Ikebuchi in 1996 at the unveiling ceremony for Hikari Kaiten Monument. At subsequent annual memorial ceremonies in Hikari, Satō gathered information about Yukiko's story and decided to write a children's book about it. In 2016 when the book was published, Yukiko Ikebuchi was in good health at the age of 94.


1. Konada and Kataoka 2006, 76-7. The Combined Fleet web site's page on IJN Submarine I-36 (accessed July 21, 2023) also indicates that Ikebuchi was the kaiten pilot who attacked Antares.

The biographical information about Nobuo Ikebuchi comes from Konada and Kataoka (2006, 249-55, 374-5) and Mediasion (2006, 85).

Sources Cited

Konada, Toshiharu, and Noriaki Kataoka. 2006. Tokkō kaiten sen: Kaiten tokkōtai taichō no kaisō (Special attack kaiten battles: Kaiten special attack corps leader's reminiscences). Tōkyō: Kōjinsha.

The Mediasion Co. 2006. Ningen gyorai kaiten (Kaiten human torpedo). Hiroshima: The Mediasion Co.