|For his video game counterpart, see Rei Saiko.|
Rei Saiko (西古レイ Saiko Rei) is an antagonist in Rockman.EXE Stream. Originally the operator of ShineMan.EXE, while desperately trying to fix a car in time for a NetNavi car race for his company, Slur.EXE turns ShineMan into Asteroid FlashMan.EXE, who promises Rei victory. After attacking other racers to win and being confronted by Netto Hikari and Enzan Ijuuin, Rei and FlashMan join the Neo WWW and begin to cause chaos and confusion in society.
Much like his video game counterpart, Rei in the anime is a member of an iteration of the WWW. However, rather than being led by Lord Wily to retrieve a Tetra Code to awaken Alpha, Rei joins the Neo WWW under Tesla where he and his Asteroid FlashMan cause havoc on society. His backstory is also fleshed out in the anime whereas in the video games he simply a follower of Wily.