Yes he is a legendary.And there is a wifi event about him in japan.
Genesect to be distributed from August 11th to September 14th over WiFi for Black 2 & White 2 only.
Pokémon Black 2 White 2 - US Genesect Event.WI-FI event The US has also just announced the Genesect event for Pokémon Black 2 & White 2. This event will download Genesect to your Pokémon Black 2 & White 2 games and will run from launch on October 7th to November 12th 2012 giving a month to receive it. It is likely to run at the same time across all English language games
Eurpoe and Australia.
(October 12 in Europe and October 11 in Australia) and lasting until November 12 (all areas), you'll be able to download over Nintendo Wi-Fi the final Pokemon in the National Dex: Genesect!