Discount ticket shops called kinker shoppu, are usually located near train stations large size cities and cities with a shinkansen stop. The discounts are usually around 5%. Although you maybe saving only 300 yen, any savings is still a savings.

These shops offer discounted tickets for highway buses, bullet trains, expressway tolls, and plane flights. These stores also sell discounted tickets to concerts, sports events, and movies. Discounted department store gift certificates and even telephone cards are sold.

Although these shops may seem shady, they are legitimate.

Because these shops are not travel agencies, you need to take the tickets you buy from them to a JR desk (midorinomadoguchi) to make a seat reservation.

A seat reservation can only be made once, but if you miss your train, you can still ride in an unreserved seat of the same day.)

During heavy travel seasons due to holidays, these shinkansen tickets will not be valid around Golden Week (4/27〜5/6), Obon (8/11〜8/20) and New Years (12/28〜1/6.)

Take a look at the savings from this discount store's website.

Joy Discount Ticket Shop - Here's a Japanese website of a shop in Aoyama.