Green tea and red bean are two very common flavour used in Japanese snacks. Green tea is probably the most well known, but red bean is starting to make waves in other parts of the world as well. For those that have never had red bean, it's actually a very sweet bean and works pretty well in desserts. Individually these two flavours should work perfectly well in a Kit Kat bar or any sweet treat. The thing is, I can't remember having ever had both of these flavours together under any circumstances.
While I'm sure it's been done, the only time I can remember having these two flavours together before was in a bowl of ice cream that had one scoop of green tea ice cream and one scoop of red bean ice cream. While the flavours did mix a little in that circumstance, for the most part they were fairly divided. I say all this because for some reason this Kit Kat tasted a little strange. I would describe this bar as being mostly green tea flavoured, in fact I would say it's more of a matcha flavour than simple green tea. Matcha is when you grind green tea into a powder and you actually drink the powdered leaves, instead of removing them after the tea is brewed. This makes for a much more intense tea flavour.
The bean flavour is there, but it doesn't taste so much like red bean as it just makes the matcha taste a little weird. That's probably the best way to describe the flavour of this bar, a little weird. It's not horrible, but it's not something I'd want to experience again and again.