There is a custom in Japan where most people do not eat food outside other than when in restaurants. However, when using the bullet train or the green car, you are permitted to eat food. Normal trains and people commuting using said trains do not permit the consumption of food whilst riding the train.

In Japan, the etiquette regarding eating on trains depends entirely on the type of train you are boarding. On long-distance trains, such as the Shinkansen (bullet train) or "Limited Express" trains that feature tray tables and forward-facing seats, eating is perfectly acceptable and widely practiced. In fact, purchasing a local "Ekiben" (station bento box) to enjoy during a Shinkansen journey is a cherished part of the Japanese travel experience. However, on local commuter trains, subways, and city buses—where seats are usually longitudinal (bench-style) and the carriages are often crowded—eating is considered a major social taboo. It is seen as inconsiderate to other passengers due to potential smells, noise, and the risk of spills in a tight space. While taking a quick sip of a drink from a resealable bottle is generally fine, consuming a sandwich or a full meal on a local Tokyo subway line will likely draw disapproving looks. The general rule of thumb is: if the train has a pull-down tray table, feel free to eat; if it looks like a typical city subway, wait until you reach your destination or find a bench on the station platform.