The Legend of Zelda: Echoes of Wisdom appears to have leaked in full a couple of days before its proper Nintendo Switch release date.
Reports from YouTubers a few weeks ago claimed that a rom containing Zelda's first solo adventure was already making the rounds, but it now seems that the rom has made its way into the hands of the general public. Echoes of Wisdom appears to have already popped up on a few prominent websites that usually host this sort of stuff, and at least one Twitch streamer has been broadcasting the game for a couple of hours already.
