This is Japanese currency we call them YEN (¥).
As of 2014 currently, $1 is approximately equivalent to ¥100.
From the upper left to the bottom, 10000, 5000,and 1000 bills of yen.
And from the upper right, 500, 100, 50, 10, 5, and 1 coins of yen.
Usually, I keep them in my pocket 5000¥ to 10000¥.
When you have a lunch, I think 500¥ to 700¥ will be good enough to have ordinary meal including coffee or tea.
From past few years, Japan has still continued the deflation, so you can find some decent meal at any restaurant when you come here. But in case of drink out, I think you should put 10000 yen into your pocket, because nobody predicts what's gonna happen after your friends and you get to be plastered. lol