Japan has a myriad of varieties of Kit Kats. Not only the regular milk chocolate kit kats, but also green tea, black tea, strawberry, orange, raspberry passionfruit, chestnut, ginger ale, mocha, creme caramel, coffee, mixed vegetable. Regular kit kat are always available. Some like green tea and mocha are available from time to time but at upredictable intervals; some appear seasonally like chestnut in autumn others like mixed vegies come and go, never to be seen again (and perhaps that's not such a bad thing...).
Usually only a couple of special varieties are available at any one time, and there's always the anticipation of what flavour can they think of next... kind of like Willy Wonka.... I was in Shinjuku on Friday and came across a tantalising collection that'd I'd not seen before: kinako (soy bean flour - often used with Japanese sweets). sweet potato, soy sauce, and WASABI!! It's kit kat season! The post office even had cherry blossom kit kats ready packaged for sending on their counter.
A nation fascinated by chocolate, novelty and seasons?
Yes on all counts, though chocolate would be last on the list. More than that, is a country captivated by word play and auspicious signs. The novelty value of Kit Kats is greatly assisted by its auspicious name. Kit Kats in Japanese sounds like Kitto Katsu. "You'll win / pass / succeed for sure! " Giving a Kit Kat at exam time is akin to a giving a good luck charm.
Green tea cherry blossom
(kitto sakura saku yo - you'll definitely pass is the message written over the cherry blossom on the LHS)
Salted caramel kitkat balls
Kobe Pudding flavour - creme caramel
Sweet potato (satsuma imo)
Soy sauce .........
I am waiting for dried bonito fish flakes ones to appear now.......