After reading chapter 74 of the Raw, now I understand why Seiichi was written as such a spineless guy. I mean, He's just too OP. He, theoretically, and practically, could adapt to any kind of environment and situation, even the Netherworld, which was a place not for the livings. And not only that, he could create any "concept" out of thin air without any restriction.
I mean, in Olga's case, it is already the world's law that the slave could only be released by its owner. But our MC "create" a "magic concept" that "erases the law". Then, could he not make a "magic concept" that "resurrects the dead"? (He already did though.) He made a subspace that has a living being in it, why wouldn't he make a new world altogether?
What is that if not playing god?
Seiichi was just too strong, the world itself asked him to not use all of his power. Since it would be too dangerous, for the world that is.
The MC got driven mad by his own strength part was good, but adding that bunny and her ridiculous purpose was a mistake.
At a certain chapter, she met the so-called Demon King. Got killed by him, or rather, by his rampaging idiot lesser dragon. Met god. Told that she got no chance to go back to her old world. Got cheat abilities. And BAM! She lived her normal daily life as if nothing happened.
Well, the currently latest chapter tells us about her getting back to Earth by chance. Though I bet she'll back to that world to meet the Prince again.