What is regret ?
Regret is the pain or sorrow felt for past actions or decisions or more precisely, the lingering feeling we have for not taking a particular action.
In that case what do people regret most ?
Not making friends ?
Not falling in love ?
Dieing a virgin ?
But for him... Leon, it was not being able to protect his childhood friend, even though he had the power to.
Reincarnated into a new world, Leon resolves to keep his powers a secret from the world however his dream was short-lived.
Reincarnating into the new world his birth caused a strange phenomenon.
Now it was only a matter of time before his identity is revealed as the one responsible for the azure moon Incident.
Overpowered ? Yes
System ? He rejects them
However unknowingly, he earns the wrath of Gods by rejecting system after system and it was only about time they strike.