The green tea that is sold here doesn't taste as powerful as the green tea Kit Kat originally brought from Japan, original green tea flavour from Japan taste more creamier, smoother, thicker and stronger, with hint of bitterness. Either way if you really want to try this, they do sell this in a packet of 12 minis in some Asian groceries, I got mine in Point Cook, some where in Highpoint shopping centre and China Town groceries do sell this.
This is a must try if you love everything green tea or Kit Kat or Both. There are a lot of unique flavours sold in Japan but I haven't had the chance to try it yet... maybe one day.
The box below was a gift from a friend who had recently came back from Japan, it contained 10 small boxes with 3 mini packets within each box. So you get 30 mini packets for about $15AUD (cheaper then here). She said it wasn't easy to find in Japan, only sold in Airports and Pharmacies I think.