The Kōfu Incident (甲府事件)

Sunday, 23 February 1975. Kamimachi, in eastern Kōfu, Yamanashi Prefecture. The sun had set at 5:36 pm. The sky was clear. Outside a housing block, two second-grade cousins were roller-skating. Katsuhiro Yamahata and Masato Kawano.

Kawano saw them first. Two orange lights over the mountain to the east. They came closer and closer, made a big turn over the Kamicho housing complex, and split. One moved away toward Mt. Atago in the north. The other stopped low, at about the height of a nearby three to four storey apartment block.

Three devices rotated on its underside. A black tube extended, clicking like a shutter. The boys left their skates behind and ran for the cemetery of Fukuōji temple. The object seemed to chase them.

Later they saw an orange glow in a grape vineyard. They thought it was a fire. Among the vine supports stood a silver craft, a dome on an inverted saucer, about 2.5 m across and 1.5 m high, though some accounts say 5 m. It rested on three short legs. Square windows glowed blue.

A hatch opened with a clank. A figure came out, about 120 to 135 cm tall, with brown, wrinkled skin, no visible eyes or nose, three silver fangs, long ears and a silver suit with a belt. It came up behind Yamahata and tapped him twice on the shoulder, making a whirring, squeaking sound, and he froze. Through the open door the boys glimpsed a second, smaller figure at a control stick among instruments flashing red, yellow, blue and green. Kawano pulled his cousin away.

They ran home, where both families were having dinner together. The mothers and Yamahata's 9-year-old older brother went back with them. In the vineyard, a dodgeball-sized orange light was blinking. It grew very bright. Then it was gone.

The next day the boys drew what they had seen on the classroom blackboard. The principal contacted the Yamanashi Nichinichi Shimbun. Teachers and reporters found a concrete trellis post broken, others tilted, and the wire mesh pressed down as if by a heavy object. A high-school electrical-engineering teacher, named in some accounts as Susumu Maeda, tested soil samples with a Geiger counter and reported radioactivity with a short half-life. Tsuneo Kira of the Japan Space Phenomena Society later reanalysed the work and pointed to phosphorus-32, which does not occur naturally.

The newspaper noted that YS-11 airliners flew over at that hour with their lights visible. Sceptics have since proposed a vineyard worker in pesticide-spraying gear, memories shaped by Ultraman aliens on television, and a craft too big to fit between the posts. No background control samples were taken for the radiation tests, and fallout from atmospheric bomb tests is another possible source. Some locals suspected the families. No formal government finding was ever made.

Researchers including Hachirō Kubota, Shin'ichirō Namiki and Kazuo Hayashi documented the case, and it is ranked beside the Kera incident among Japan's great UFO cases. The association UFOKOFU1975 registered 23 February as Kōfu UFO Day. About 100 people attended the 50th-anniversary event in 2025, with Yamahata on stage. "It scared the life out of me back then," he has said.