a boy/girlfriend and money; finger counting is also different
when someone is talking about someone else's boy/girlfriend they might not say the wooooord, but use their little finger up. Easy to do, close your hand, fingers looking towards you and raise the little finger. Everyone will understand.
Money. In Europe, we use the thumb and the forefinger in a mouvement that simulates money touching and counting. Well, sort of. In Japan, you want to show a coin. Easy: put your hand in front of you, the palm towards your feet or the person you are talking to. Join the point of the nails of your thumb and finger so that it creates a round, facing you. Keep the 3 other fingers souple but extended. Then, you need to rotate your hand, the little fingers coming toward your belly so that your two thumb and your fingers will face outward. I am not sure that this is clear.
Finger counting: for those mathematically challenged people, finger counting is very important. In Europe, 1 is the thumb, 2 is made with the forefinger+ middle finger, 3 is thumb+forefinger+middle finger, 4 is all fingers minus the thumb, 5 is composed of 5 fingers, and then you go on with your second hand until 10.
In Japan, this is totally different. First of all, you will use only one hand to count until 10. Easy: get your hand in front of you, palm up. sounds like yoga. You will close your hand one finger by one finger to get a gist at 5.
1: put your thumb inside the palm, 2: get the forefinger above your thumb. 3, get the middle finger on your thumb etc. 6: you open your hand again, starting with the little finger, so that 10 is the hand open.
if you show numbers to people, for instance in a restaurant, to tell the waiter how many of you there are, this is different. 1: the forefinger is raised. 2, forefinger+ thumb. 3: forefinger+middle finger+ ring finger;
but the english way is fine too it just does not feel Japanese.