The Shinkansen, Japan's high-speed "bullet train," is busiest during the morning and evening rush hours, specifically between 7:30 AM to 9:30 AM and 5:00 PM to 8:00 PM on weekdays. During these windows, business travelers clog the Nozomi and Hikari lines, especially on the Tokaido Shinkansen route between Tokyo, Nagoya, and Osaka. Furthermore, Sunday evenings are notoriously crowded as people return to the cities after weekend trips. On a seasonal level, the trains reach peak capacity during "Golden Week" (late April/early May), the Obon festival in mid-August, and the New Year holiday period. During these times, even the non-reserved cars can have standing-room-only conditions. If you are traveling with large luggage or want a guaranteed seat, it is highly recommended to book a reserved seat well in advance or travel during the "mid-day" lull between 10:30 AM and 3:30 PM.