Will Japan be submerged by the Pacific Ocean?

This question needs to be looked at from two perspectives: one is sea level rise, and the other is crustal movement. Overall, the possibility of the entire country of Japan being submerged by the Pacific Ocean is virtually zero in the foreseeable future.

First, let's talk about sea level rise. This is indeed a global problem, as global warming and melting glaciers are causing sea levels to gradually rise. For island nations like Japan, especially some low-lying coastal megacities such as Tokyo and Osaka, they will certainly face greater flood risks in the future and will need to spend a lot of money to build higher dikes to cope. However, this is like a faucet in a bathtub that isn't fully turned off; the water level is slowly rising, and it will flood the low-lying areas near the drain. But to submerge the entire toy duck (the whole of Japan) in the bathtub, the amount of water and time required would be unimaginable. Most of Japan's land is mountainous and hilly, with sufficiently high altitudes. Therefore, sea level rise will only "erode" its coastal areas; submerging the entire country is not possible.

Next is crustal movement. Many people might have seen the movie or read the novel called "Japan Sinks," where the plot involves the entire country of Japan sliding into an oceanic trench due to drastic crustal shifts. The origin of this idea is that Japan is indeed located at one of Earth's most active plate boundaries—where the Pacific Plate is slowly "drilling" beneath the Eurasian Plate, a process called "subduction."

However, "subduction" does not equal "sinking." This geological process is extremely slow, occurring at a rate of a few centimeters per year. Moreover, the process of plate compression, while subducting, also causes the uplift and folding of the continental plate, which is precisely why Japan is mountainous, earthquake-prone, and volcanic. It is a dynamic process with "give and take," not a unilateral pulling down of Japan. For a landmass the size of the Japanese archipelago to sink into the Mariana Trench in a short period, the energy and geological changes required would be catastrophic, and it's virtually impossible in reality.

So, to summarize:

Sea level rise is a real threat, but it will only affect Japan's low-lying coastal areas, not the entire country. Crustal movement leading to "Japan Sinks" is more like a science fiction premise; real-world geological changes are measured in millions of years, so we don't need to worry about this in our lifetime.