Despite becoming a monster to most to save those that he loved and his world, he lost it all.
After years of research and trying to find a way to undo the loss and failing.
Knowing she'd be ashamed if he ended his life for no reason.
He followed the legends of a way to be reincarnated, but not into his own world.
A type of reverse summoning.
If he couldn't save this one and those he loved, he would damn well make sure that it wouldn't happen again.
He would stop the encroaching Darkness and the horrors it brings in a new world.
And if he died completing it....
She wouldn't be ashamed.