I think Herm getting killed in front of Robert would also be devastating because it’d make him realize he wasted his life being fixated on stopping Shroud
in the dating since teens au, i imagine robert getting so fixated on the ides of stopping shroud (he thought he was doing something good, something to protect herm and beef, but in this scenario it ends up backfiring him), he would leave herman and beef alone a lot. whether it's night or day, if he needs to go on a mission, he will leave. even though him and herm are a hero duo as mecha man and waterboy, robert never lets herm go on more serious missions with him, because he's afraid herm will get hurt.
so seeing him getting killed right in front of him, made robert realize that he fucked up. he spent so much time chasing after shroud, he didn't even have a proper conversation with herman before his death. herm died thinking robert was getting bored or annoyed with him, and that was the reason why he was always leaving him and beef.
this is why he feels so much guilt over it. he apologizes over herman's grave so much. tell him he loves him, how he misses him. knowing that herm probably doesn't hear him.
