Since it's an important custom to take off shoes indoors in Japan, you might need to take off your shoes often. Bringing a pair of shoes that you can slip off and on easily might be convenient. Also, make sure to bring and wear a nice pair of socks to avoid any embarrassment.It's convenient to bring major credit cards, such as MasterCard or VISA. You can use them at various places, such as department stores, major stores, hotels, and restaurants. Small stores might not accept credit cards/traveler's checks, especially in rural areas. It's good to carry some Japanese yen in cash while you are in Japan.
For information about restricted items, please refer to Japan Customs Procedures by the Ministry of Finance Japan