Did the Japanese government push for constitutional reform because the U.S. military already decided to withdraw from Japan? No, that's not true: There are no plans at the time of writing from the U.S. and Japan to close U.S. military bases around Japan, and there is no evidence that Article 9, or the "no war" clause, of the current Japanese Constitution will be amended in the near future.
The claim appeared on TikTok (archived here) on October 26, 2023. In a video, a man claims that the U.S. military has already made the decision to withdraw, and the media isn't reporting on the issue for strategic reasons. The caption reads (translated from Japanese by Lead Stories Staff):
The truth behind Article 9's revision is to let the US military retreat from Japan!!
This is what the post looked like on TikTok at the time of writing:
(Source: TikTok screenshot taken on Thu Nov 2 02:40:20 2023 UTC)
Article 9 of the 1947 Japanese Constitution, known as the "no war" clause, outlaws war as a means to settle international disputes. It also says that armed forces with war potential will not be maintained. This led to the Japan-U.S. Security Treaty in 1951, which was replaced in 1960 by a new version. It permits the presence of U.S. military bases on Japanese territory and obliges the two nations to defend each other if one or the other is attacked "in the territories under the administration of Japan."
The interpretation and possible reform of Article 9 is an ongoing debate in the government and in public since its adoption. After former Prime Minister Shinzo Abe reinterpreted Article 9 in 2014, the Japanese Self-Defense Forces (JSDF) gained the right to participate in collective self-defense.
After Abe's resignation in 2020, his agenda to fully revise Article 9 was pursued by his proteges such as current Prime Minister Fumio Kishida. Nonetheless, no progress has been made as of this writing. There were not enough votes in the National Diet [the national legislature of Japan] to pass the motion to revise Article 9, and thus the terms of the U.S.-Japan Security Treaty are still enforced. Additionally, effective as of April 2023, Japan has approved five more years of funding accommodations for the U.S. military's stay in Japan following threats from neighboring countries such as North Korea. There is no evidence that the U.S. military has decided to leave Japan anytime soon.