The Plain Salary Man Turned Out to Be a Hero: He Was Invincible, Only to Be Exposed on His Niece's Dungeon Stream - Ch. 23

[MangaDex]

 

[brndndss]

MC under so much stress, whoever this muscular challenger is just gonna crushed like a bug

 

[welcome2atlantis]

So when under stress, MC's body grows larger and muscular.
If I had this trait, I'd be Hulk.

 

[Churkey]

YOU try to work overtime without 3 days of rest and see if you're the strongest huh!?