On the metro in a big city it is frowned upon. On the shinkansen or other distance express trains it is encouraged. The stations even sell Ekiben (station food boxes) and the shinkansen has a foodcart that sells ekiben, snacks and drinks (incl. sake and beer).

In Tokyo, eating on the subway or local commuter trains is strongly discouraged and considered a major breach of social etiquette, though it is not strictly illegal. Japanese culture prioritizes omoiyari (consideration for others), and the smells, sounds, and potential mess of eating are viewed as a "nuisance" to fellow passengers in the often-crowded, silent cars. Drinking water or tea from a re-sealable bottle is generally acceptable, but eating a meal—even a small snack—is rare. The major exception to this rule is long-distance trains like the Shinkansen (Bullet Train) or "Limited Express" trains (like the Romancecar), where seats have tray tables and eating ekiben (station bento boxes) is a celebrated part of the travel experience. For local subway lines like the Ginza or Marunouchi, it is best to finish your food on the platform or at a convenience store before boarding to avoid the disapproving stares of local commuters who value the cleanliness and quiet of their public transit system.