Board Thread:Questions and Answers/@comment-30751547-20170207174415/@comment-79.68.55.120-20170527185258

Chances are Blast is actually just the cyborg dude, got captured and converted into a crazy ass cyborg, that's why nobody knows where he is. I highly doubt there is any relation between him and Saitama, but if I'd say he must have met Saitama at some point at least, is my guess.