Udgey said:
The author actually just ruined this manga for me. Huge suspension of disbelief. That's just not possible for nerdo here to kick everybody's asses when a few chapters ago he was getting his ass kicked by fodder punks.
For starters, suspension of disbelief is the usual mindset of believing what's going on in the work; what you want to say is that he ruined your suspension of disbelief, not that you had one. Or that there is a huge plot hole, maybe. I don't know to what extent you butchered the phrase in your head.
The other thing is that it was obviously an act. He wasn't getting bullied, it's thoroughly explained that he wanted to get everyone to trust him, hence the "I'm a poor kid getting bullied" act.
Mod Edit: Removed insult.