Buy gourmet sweets, candies and chocolates as thank you gifts. The Japanese like gifts of exotic or handmade candy or chocolate. Don't forget dietary restrictions when selecting food gifts for a Japanese host or friend. Get the gifts professionally wrapped for a good presentation.
The Japanese prefer gourmet liquor to the common variety and like fine whiskey and bourbon. A gift of exotic wine or spirit from your home country to say thank you shows your thoughtfulness in carrying it all the way from home. Alternatively, buying good local wine will win you extra points, because that shows an appreciation of the Japanese products. Seek the help of the sales person in the store if you are not sure of what to buy. Leave store labels or anything that indicates the store name, because a more expensive store hints at a better gift; the reverse is also true.
Many Japanese fruits like Fuji apples or the Asian pears make common thank you gifts. Sometimes fruits are individually wrapped in protective casing, within a larger box; it makes the whole ensemble look stylish.
Green tea is associated with funerals and does not usually make an appropriate gift. However, gourmet coffee beans and black tea are fine.
Present gifts of money in a special Japanese envelope called "noshibukuro." Different occasions in Japan, call for different colors of cord and ways of tying a "noshibukuro". Tie your "noshibukuro" with a red and white colored bow when the gift is a thank you gift. Don't give gifts in multiples of four and nine because the Japanese words for number four and nine mean death and suffering respectively. Be extra careful with this because such mistakes are not easily excused.
Never give white flowers because they are related to funerals, especially lilies, camellias and lotus. Arrange the flowers extensively to show that you are really thoughtful. Many flower shops commonly exhibit the Japanese art of flower decoration (called "Ikebana"). Avail the sales person's assistance to get the flowers professionally arranged.
Avoid giving a potted plant; the Japanese consider them bad luck. Bonsais are acceptable as gifts, however. A bonsai thank you gift symbolizes a nurtured relationship. The roots of the bonsai symbolize a long and lasting association.