Most of the tutorials are outdated. But someone named Sadadsdf (or safdfwq) properly explained how to get it in a reply to a comment on a video. Play Stick it to the stickman Demo (and wishlist it bozo.): store.steampow...
To make a long story short, you basically do 100 Squats, Sit ups and Push ups in the gym. (You don't have to run around, just do 100 of the 3 things.) And badabing, badaboom, you have Saitama. The reason why it doesn't say I didn't get it when I did 100 of everything is because I already did this. Hence why this video even exists.
