While the Suica card is incredibly versatile in 2026, it is not a "magic key" for every corner of Japan. You generally cannot use it for continuous travel between different IC card regions (e.g., you cannot tap in at a station in Tokyo and tap out at a station in Osaka or Sendai). If you cross regional boundaries, you must use a paper ticket or settle the fare with a station attendant. Additionally, it cannot be used on most Shinkansen (bullet trains) or "Limited Express" trains without a separate reserved-seat ticket. Some very remote rural bus lines and "themed" local railways in areas like Shikoku or northern Hokkaido still only accept cash. In terms of retail, you cannot use it at stores within the PiTaPa area (Kansai region) that do not support the "mutual use" logo, nor can you use it for specific high-value transactions or at most government offices.