His return to New Zealand followed the publication of a story in The Daily Telegraph this morning which alleged the married All Black had a relationship with a former Australian model.
NZR said it could not comment on the Kaino allegations or further details about Aaron Smith's personal life which were published today as both were "personal matters".
But NZR said it felt for all of those affected.
Chief Executive Steve Tew said the NZR understood that the game and players were under public scrutiny and these latest stories in the media were concerning.