We have talking about a mystery 5-inch smartphone from HTC for weeks now, with leaks coming thick and fast. Now it's here, although the HTC J Butterfly is (annoyingly) a Japan-only launch so far.The key words there are 'so far'. There is no reason why this smartphone will not see a wider launch. Previous rumours hinted at this being one of the upcoming Google phones, so don't rule that out just yet.For now though, let's concentrate on the phone as it stands, which is a pretty impressive piece of kit that's hitting the Japanese network KDDI in December. The J Butterfly is a premium model for sure, with a 5-inch, 440ppi full-HD Super LCD 3 screen and a 1.5GHz quad-core Qualcomm APQ8064 processor, running Android 4.1 Jelly Bean for the operating system.Also present is an eight-megapixel camera that shoots 1080p video, a 2.1-megapixel front-facing camera, 2GB RAM, 16GB of internal storage (a microSD slot will expand this), Bluetooth 4.0, NFC and LTE connectivity. Oh yes, it's also waterproof, which is a useful feature if you are one of those people who really can't walk down a street without having a phone fixed to your ear.The colour choice is red, white or black and the hope is that we'll get a version of this in the UK before the year is out, which will probably be under a slightly amended name. Updates as and when any news breaks.