
How did he turn back time? How did both Jade and Viche regress? What happened after Viche died in the second life?

We don't know yet but it can be:
-He loved her so much more in it's previous life that instead of being lovey-dovey with the saintess, he tried to 'reverse time' for save her. If it the case, she keeps her memory because she was 'protect' by 'god' (the one who bring her) in the first place. It seems to know a Wizard (the one he want him for tutor), so he used magic and reach him for futur plot to save her (he seems willing to come because ML trow a great bait)
-The story didn't follow the right path because the ML didn't forget her at some point and the Saintness wasn't able to save him. So the 'God' reverse the clock another time. ML keep is memory by the 'power of love' bullshit that keep happening in romance novel. :p
I hope it more close to the first one, but sometime Authors can be lazy so they go with the 'Power of love' shenanigan.
Can't wait for season 2! This is definitely a favorite