I know MC fears death with all his soul and he got ripped apart this time so it traumatized him even more, but it feels like he is getting weaker in his willpower after resurrecting.
There are stories with the MC having to kill some immortal bad guys over and over to make them cancel the ability on their own, he feels like them, a real MC would endure.
Just to say, he got killed in painful ways multiple times to get the inversion skill, but it was enough to be ripped apart once to not even have the willpower of helping the girls.
On another note, many characters in this story are stupid, MC first, the girl that entered a boss room where their immortal friend was just kidnapped out of worry even more.
Not to forget how some simple simple roaming enemies in the death tower gave them problems and they decided to challenge the fucking boss of the death curse spawning place.
Note, MC is not in a urge of getting money or power, he doesn't have anyone that needs it as just getting some money made him go waste it.
The girls too like to adventure but there was no reason whatsover for them to challenge the death tower.
Unfortunately this author story building is terrible, as MC is immortal he had to give him weak points being friends and fear of pain.
This characters would be the first to die in similar stories if not for deus ex machina.
The problem is that MC way to raise in power is simply to bite it for a while, but he doesn't want to, he have nothing urging him to get stronger so challenging difficult places make no sense and there is no stake as to put him down he should have to deactivate the skill, fall in some impossible to escape trap or get assassinated outside the towers.