Stream continues the storyline set by Axess by introducing Duo, a being from outer space who seeks to destroy humanity after witnessing the chaos caused by Dr. Regal. Intrigued by Cross Fusion, he decides to spare mankind temporarily, bestowing a test upon the main characters to assess whether or not humans truly merit survival. He sends his subordinate, Slur, to Earth, where she hands Navis possessing the powers of Duo's asteroid to unsuspecting people to observe what they will do with such might. Lan (Netto) and the other net saviors must work together to foil Duo and his subordinate. In the process, Neo WWW is formed by Tesla Gauss (Tesla Magnets) to cause havoc. Dr. Regal also returns during the movie, and again towards the end of Stream, with the focus of Stream shifting to time travel.