PvP in Nioh is covered on this page. PvP will be released as a DLC shortly after the game's launch. This page will be updated when more is known. Players can check out the Builds page for ideas in crafting optimal setups.
PvP will be releasing on May 2nd for players. There are no details as to what form PvP will be, whether it's environmental like in Dark Souls or if it's a separate sparring dojo. This page will be updated with details as they are revealed.