I’ve lived in Japan—in and near Tokyo—for four decades, and on the trips I’ve made to Seoul I’ve enjoyed observing similarities and differences between the two cities. One of the differences was uniformed soldiers riding the subway in Seoul, something I’ve never seen in Tokyo. Another was what looked like emergency supplies stored on subway platforms; I’m guessing they were there in case the subways had to be used as bomb shelters. (I can’t read Korean, so I might have misidentified the items or their purpose.)
Postwar Japan has done a lot of preparation for natural disasters but has had essentially no civil defense measures against military threats. That might be changing, though. Just a couple of weeks ago, for the first time, the city of Tokyo designated 105 subway stations as emergency evacuation sites in case of missile attacks [1, in Japanese]. This was prompted not only by the continued threat from North Korea but also by what has been happening in Ukraine.
Disaster preparedness is different from feeling threatened. Visiting Seoul rubs off differently than actually living there. For instance, seeing military men on the subway is nothing out of the ordinary to Koreans because military service is compulsory. To outsiders, it may evoke images of heightened threat or militarism. To insiders, it's "oh hey, it's some young men."
I am tempted to speculate that the average Japanese civilian is more worried about the threat of North Korea than the average Korean civilian.
Postwar Japan has done a lot of preparation for natural disasters but has had essentially no civil defense measures against military threats. That might be changing, though. Just a couple of weeks ago, for the first time, the city of Tokyo designated 105 subway stations as emergency evacuation sites in case of missile attacks [1, in Japanese]. This was prompted not only by the continued threat from North Korea but also by what has been happening in Ukraine.
[1] https://news.yahoo.co.jp/articles/34fd48f39ee9b8a78197f350e8...