Regarding the U.S. government’s directive ordering Anthropic to suspend access to “Mythos” and “Fable” from outside the United States, Japan’s Finance Minister Satsuki Katayama posted on X (formerly Twitter) on June 13 that “as of now, there has been no change in the situation as understood between the finance ministries of Japan and the United States.”
At her post-cabinet press conference on the 16th, Katayama likewise signaled that the suspension itself would have little impact.
This article reviews the developments to date concerning Japan’s access to Mythos, together with what Katayama said on the 16th.
From Mythos’s Opening to Japan to the Suspension of Access
Mythos, developed by Anthropic, detects cyber vulnerabilities said to be difficult for humans to spot easily. In May, the Japanese government asked U.S. authorities—including Treasury Secretary Scott Bessent, who was visiting Japan at the time—to grant Japan access to Mythos. Then, on the 2nd of this month, Katayama announced that access to Mythos Preview had become possible.
For the full background, see the following:
On the 12th, however, the U.S. government instructed Anthropic to suspend foreign nationals’ access to Mythos. The reason given was export control stemming from national security concerns. Anthropic complied.
Katayama’s Remarks in Detail
Here, the author examines the current state of Japan’s access on the basis of Katayama’s comments on the 16th.
Katayama stated: “Japan began building a testing environment comparatively early by global standards. We had already started the exchanges needed for that, so whether or not those exchanges are suspended is not a particularly significant problem.” This is consistent with her post on X that “there has been no change in the situation as understood between the finance ministries of Japan and the United States.” In other words, it is the Japanese government’s understanding that the U.S. government’s recognition of Japan’s access to Mythos remains unchanged.
At the same time, Katayama also noted that “it has been pointed out that the risk may have increased because Mythos 5 and Fable 5 were released to the entire world for three days.” That is, the release gave rise to a risk of misuse. On this point, Katayama said plainly that “this will also be discussed at the summit on the 17th,” suggesting her expectation that matters would move forward.
She further emphasized—with respect to both Mythos and OpenAI’s most advanced model—that “it would be enough for the U.S. government to grant Japan most-favored-nation treatment” and that “the question is whether the risk (of misuse) has increased,” underscoring that consultations between Japan and the United States are continuing on this point as well.
Judging from the Japanese side’s comments alone, the current suspension appears to be a temporary security measure, leaving open the possibility that access will resume in the future. At the coming summit, Prime Minister Sanae Takaichi may reaffirm this understanding.
