The vast majority of Japanese trains have so-called non-reserved (or unreserved) seats (自由席, literally "free seats"), which do not allow reservation and are available on a first-come, first-served basis. However, some trains have only reserved seats (指定席), which require prior reservation. What are the most prominent ones, and how to find out whether a given train has non-reserved seats?
First a reminder: whether one posseses a rail pass such as the Japan Rail Pass has no effect on seat reservation requirements. If reservation is required, it remains so if you have a rail pass. Of course, a rail pass usually allows you to make reservations free of charge, but it is still necessary to visit the ticket office to make your reservation. (Note that some minor regional passes do not allow you to make reservations; in that case all-reserved trains require payment of at least the reservation fee.)
Firstly, there are four all-reserved Shinkansen services. Note that all services on the Tokaido-Sanyo-Kyushu Shinkansen between Tokyo and Kagoshima-Chuo, serving Nagoya, Kyoto, Osaka, Hiroshima, Fukuoka, Kumamoto, etc. have non-reserved seats.
- The Hayate and Hayabusa services on the Tohoku-Hokkaido Shinkansen between Tokyo and Shin-Hakodate-Hokuto.
- The Komachi services on the Akita Shinkansen between Tokyo and Akita.
- The Kagayaki services on the Hokuriku Shinkansen between Tokyo and Kanazawa.
If you try to make a reservation on one of those trains and the train is fully booked, you will have the option to obtain a standing ticket, which as its name implies lets you ride the train by standing in the intervals between carriages. A standing ticket is slightly cheaper than a reserved seat ticket, as it does not include the seat reservation fee. It is not possible to obtain a standing ticket in any other circumstance, such as if the train is not fully booked (in order to save money) or on any train other than the four above.
The two "premium" express services serving Narita airport are also all-reserved:
- The JR Narita Express, serving many stations in the greater Tokyo area.
- The Keisei Skyliner, serving Nippori and Ueno.
The two surviving regularly scheduled overnight trains:
- The Sunrise Seto, between Tokyo and Takamatsu.
- The Sunrise Izumo, between Tokyo and Izumoshi.
Finally, almost all "touristy" trains are all-reserved, such as:
- The Resort Shirakami, along the Sea of Japan coast of Aomori and Akita prefectures.
- The POKÉMON with YOU, between Ichinoseki and Kesennuma.
- The Yufuin no Mori, between Fukuoka and Beppu.
- The SL Hitoyoshi, between Kumamoto and Hitoyoshi.
- and many more...
The easiest way to find out whether a given train has unreserved seats (or, in general, which seating options are available on it) is to look it up on Hyperdia, and see what options are available in the drop-down list of the "Seat Fee" column. If the column is empty, it means the train is an ordinary commuter train, where reservation is not possible in the first place.