I'm not sure it would cause offense if you tried, but Japanese staff would refuse politely if you tried to give them a tip. Tips are not given in Japan, which made things so much more pleasurable and easier I found, not to worry about that sort of thing in return for excellent customer service (I have never had a bad experience)! The only example of a tip that I've seen is at a traditional Geisha house, where people traditionally give smart little envelopes with a bit of money in them as a thank-you to the Geikos for there company.

http://www.whototip.net/tipping-in-japan https://ja.wikipedia.org/wiki/%E3%83%81%E3%83%83%E3%83%97_%28%E3%82%B5%E3%83%BC%E3%83%93%E3%82%B9%29 https://en.wikipedia.org/wiki/Gratuity http://matadornetwork.com/abroad/10-japanese-customs-you-must-know-before-a-trip-to-japan/ http://goasia.about.com/od/Customs-and-Traditions/qt/Tipping-in-Japan.htm http://www.japan-talk.com/jt/new/why-you-shouldnt-tip-in-Japan http://www.news.com.au/travel/travel-advice/where-tipping-is-actually-considered-rude/story-e6frfqfr-1226701085391 http://www.annieandre.com/2013/01/countries-where-you-dont-need-to-tip/