Looks like it may have to do with Israel. I googled how much Japan has given to Palestine and it's nearly 1B over the years, much of it through the UNRWA. They've also given a lot of aid to Palestine after 10/7, with the Japanese envoy warning it was going to Hamas. From 2/10 Jerusalem Post article:
Japan's rocky road and balancing act with Israel during Hamas war
Foreign affairs: Conflicting messages have come from Japan regarding its support for Israel since the beginning of Israel's war against Hamas.
Nissim Otmazgin, a Japan expert at the Hebrew University who is the dean of its humanities faculty, cited Japan’s initially very mild statement and noted that the tone in Tokyo changed and became much more clearly supportive of Israel after US President Joe Biden gave his strong pro-Israel speech on October 10. The change in tone, he said, was “definitely because of the American factor.” Once it became clear where the Americans stood on the issue, Japan fell in line.
...
"The relationship with the United States is the most important thing for Japan’s foreign ministry,” he said. “It is out of that relationship that Japan’s relationship with Israel emerges. We have to look at Japan’s relationship with Israel as part of the wider relationship with the United States.”
Otmazgin said that Israel will need to lean into its relationship with the US to prevent a negative development in the Japanese-Israeli relationship that unfolded this week from snowballing: the announcement by Itochu, Japan’s mammoth trading and investment company, that it was severing its aviation unit’s strategic cooperation with Elbit Systems as a result of the war. Itochu was ranked 96 on the 2023 list of Fortune Global 500 companies."
..
"The fear is that because of the war, Israel’s image as the Start-Up Nation will slowly fade away and Japanese companies will start withdrawing from the Israeli market,” Otmazgin said, terming Itochu’s move as “very unfortunate.” "
https://www.jpost.com/israel-hamas-war/article-785955
So, perhaps a hand slapping from Biden.