"Finally it's here, a Bayonetta game on PC and it's free ! Download the game : http://steamproxy.net/steamstore/app/567090/
Apparently there is a hidden URL in the achievements : http://www.sega.com/14111219 source : Steam community.

SEGA’s favourite Umbran Witch climaxes her way onto PC! Thrill to her signature beehive do in 8-bit pixelated glory! Jump! Shoot! Score! Being bad never felt so retro."