To understand Japanese customers you need continued exposure to see the behaviours and changes

Book: Japanese Culture

Review:

"By far the best overall coverage of Japanese cultural history-- cogent, intelligent, readable,"

By Zangiku

" Ethnography involves prolonged participation within a specific culture or sub-culture" 

Source: Goulding. C. (2004) Grounded theory, ethnography and phenomenology, 

European Journal of Marketing, 

Volume 39, pp 294-308.