It was interesting to read that. Of course you can't start doing that kind of workout right off the bat. You need to work up to it! Also, of course the workout regimine from "One Punch Man" isn't well balanced, he is training to be able to punch well, not focused on general health.
Are people seriously just jumping into this routine as a means of getting fit?
Started my fitness journey during covid and one thing I can recommend which is non-obvious to those who haven't been training all their lives is progressive overload:
If you're doing 20 pushups this month, do 21 next month, then 22 the month after, etc. Keep pushing yourself and you'll get stronger than you ever though possible. Take it at your own pace though, if you push too hard it's easy to hurt yourself.