[Another One of japans "Big 3" Ufo cases: as such it was covered & sensationalized in magazines, books & comics in the '70s & '80s, the encounter took place during the height of the global "humanoid aliens" boom. - Once again; I've decided to paraphrase the story & information from various reliable English & Japanese sources. Please enjoy! ]
• About this alien: an example of a B.E.A (Big-Eared-Alien) with a brown wrinkly face and 3 tusk-like fangs, it was wearing all silver, a jumpsuit which connected to its head which had no eyes or nose, making it resemble a mask. (At one point they compared it to a nopperabo.) it had long, rabbit-like ears that had something like holes in the middle. it was carrying a ray gun with a tip that looked something like a trumpet, and it had boots with two toes, that split down the middle (similar to a farmers jikatabi boots.)
• The Encounter: On Sunday, February 23, 1975 in Kami-Cho, Kofu City, Yamanashi Prefecture, Japan, at about 6:30: Two 7-year-old elementary school kids, Katsuhiro & Masato (cousins) were out late on their way home after a day out playing.
The witnesses: Katsuhiro Yamahata (left) and Masato Kono (right) - Source: Junichi Yaoi (July 1978). Zenkoku UFO Mokugeki Tahatsu Chitai(UFO Sighting Zones in Japan), 194-197, Futami Shobo.
Suddenly, a bright orange UFO about the size of a passanger car, had flown low overhead of them, they saw that the bottom of the ufo had what they interpreted as a 'gun-like' weapon: so they retreated, hiding in the graveyard of the nearby Fukuoji temple.
There they lost sight of the UFO, continuing on their way, the light appeared again as it landed in the nearby grape vineyard: a bright fire-like glow had appeared in the distance, although they were terrified, they were also excited and curious young men, so they went to go see if it had crashed.
The curious boys entered the vineyard and observed the still ufo for about 5 minutes, it had destroyed some nearby cement columns [later it was said that the boys would have been unable to do this themselves.] - They described the ship as a domed silver craft with 3 round landing gears, Masato was able to recount what he interpreted to be black slightly raised (sticker-like) "Space text" on the front side of the craft. Katsuhiro decided to go to the west end of the ship, there was another word which resembled connected letters like "A..B..C..." [when trying to recount it, he couldn't remember the rest.]
Suddenly the doors [to the right of the text] slid open and a staircase fell out: a very spindly passenger with a deeply wrinkled face emerged from the vessels stairs right in front of Masato, Behind him inside the dimly lit craft, he noticed another alien inside sitting in front of a screen. Masato was suddenly hit with overwhelming dread.
• Witness sketches of the Alien, crafts and raygun. (June 1975, "UFOs & Space.")
at the same time, behind the craft, Katsuhiro was tapped on the shoulder by a second identical-looking alien who came up from behind him: The alien cried out in a strangely squeaky voice (that sounded like a bird or like a tape recorder being fast-forwarded) however, they could not understand what it had said. -- Noticing the gun: terrified, he lay down in fear and played dead.
Masato ran out from the front of the ship, thinking quickly, he grabbed Katsuhiro and threw him over his back, the two then quickly retreated!!! - returning later with their parents. They where quite skeptical & scolded them at first, but came around when they returned to the scene: Though the aliens were gone, they saw the same orange glow, the family described it as a brilliant flare “similar to a hitodama” in the vineyard...
The next day in class, the boys drew pictures of what they had seen and boys told their school friends about it: their teacher, knowing that they weren’t the lying types, decided to contact the news. - Soon after, the encounter became a hot topic with several officials & entering the vinyard and running tests.
Soon after, the kids where questioned by their school, their parents, police and notably, ufo investigator: Masaru Mori. Most of the Interviewers said that The boys stories were remarkably consistent. - Unsurprisingly the authorities denied everything.
The owner of the field at the time was interviewed numerous times by TV, newspapers, magazines, and other media however, his statements were never recorded or reported on. [likely because his story didn't align with what the witnesses said happened.] -
Unfortunately, there's also no photo evidence from the encounter either.
However: The case is often considered somewhat credible because a specialist tested the area's topsoil: after about a month of tests, it tested positive for artificial radioactivity: the result came back positive for radioactive isotopes with short half-lives [More info about that can be read about here.]