Many bikes aren't locked at all. Those that are secured are locked with a thin cable or chain. Some bikes have a lock on the fork or frame that inserts a metal bar into the spokes, preventing movement. Some high-end bikes have a heavier chain. A major motivation for the broad use of bicycles is economic.
Cars are expensive to own and operate in Japan.
Despite the high-cost, car ownership continues to grow in Japan. Nearly five million people drive everyday in the Osaka Perfecture, a 400 percent increase since 1960. A visit to Osaka is very refreshing for a US bike activist. Imagine observing hundreds of mature, well-dressed men and women riding a chari to work or shopping. What an inspiring argument for the propriety, rationality and sensibility of cycling.