Domestic flights
For very long distances or to reach the islands, the plane beats the train. The flag carriers are ANA and JAL, alongside the low-cost airlines Peach, Jetstar Japan and ZIPAIR. A Tokyo–Sapporo (Hokkaido) or Tokyo–Okinawa is much faster by plane than by train, and booking weeks ahead the low-cost airlines offer fares that can drop below 30–60 € per leg. Both ANA and JAL have domestic flight passes for foreign tourists (ANA Experience Japan Fare, JAL Explorer Pass) with very competitive flat fares on long routes. For Hokkaido, Okinawa or southern Kyushu, always compare flying versus the Shinkansen.
Ferries
Japan is an archipelago, so ferries cover routes the train cannot reach: between islands of the Seto Inland Sea, towards Hokkaido, the Okinawa islands or small destinations. Most tourists only use short, very specific ferries, such as the JR ferry to Miyajima (included in the JR Pass) off Hiroshima, or the boats of the Hakone loop on Lake Ashi. For long crossings between islands there are overnight ferries with cabins, a cheap but slow alternative.
Taxis
Taxis in Japan are safe, clean and honest (they do not inflate the price), but expensive for continuous use. The flag fall is around 500–700 ¥ and each kilometre adds about 100–150 ¥, so a 10 km urban trip can easily cost 30–40 €. They make sense for heavy luggage, destinations with no metro at night, or when there are four of you and the fare is split. The GO app lets you order a taxi in almost the whole country with an English interface and card payment.