However, the situation you describe above with uncomfortable seats and necessity of detailed train schedule knowledge will hardly be a topic if using Seishun 18 on the Tokaido Line btw. Tokyo and Kyoto. Those trains are all new and the schedule is quite frequent with only relatively short waiting times. At least that’s what I remember from my last Seishun 18 trip from Tokyo to Maibara 3 to 4 years ago. The situation is however quite different if you’re travelling rural areas like Hokkaido, Shikoku or Hokuriku.