True. In Jihan's previous life, Sae Ah died. She died because of sword king's fanatic fans. Because that sword king left her. No matter what happened, it's a fact that if it's not for current Jihan, Sae Ah would have die again.
I believe the only reason he able to come to his sense was thanks to that time Jihan exposing Shizuru's ability.
Spoilers about Sae Ah's previous time-line death
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Actually no. In the previous time-line she died because of that other girl with the late-bloomer gift. Yes, she was attacked by the crazy fans, but no she didn't commit suicide because of it, in the hospital while she was recovering one of the subordinates of that Russian girl entered the room, his ability makes him capable of controlling people's minds, and he forces her to jump. She was recovering pretty well actually at that moment.
This will appear at some point when they go to one of the places dominated by those gates and the Void energy, and they are able to see glimpses of the life on the previous time-line.
Spoilers about Sejin's return and some times about the previous time-line
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Well, when he gets back to normal, post-brainwashing, Sae Ah is actually pretty happy she has her father back to normal. And his relationship with Ji-han is preety okay. They have really funny moments actually.
The fact is he was brainwashed, a lot of the decision he made wasn't done in sound mind either, Shizuru had to use three skills to keep him locked to way he is know, and she can't leave his side to keep her control on him, if she leaves even for a few hours her control of him weakens. And the fact she took him away from his daughter is because his love for his daughter renders her control weaker.
In the previous life-time he was only able to break out of the control of Shizuru when they faught against the elves and was hit with a sword made of the World-Tree's branch, that nullifies status abnormalities (which is what Shizuru does - it's a status abnormality). But was already too late, that's why he disappears in the fiuture Ji-han came from, he killed Shizuru there and the went to the Void/Dungeon places looking for his wife, and thenhe becomes a monster of the end kind of thing because he wanted to be punished because of what happened to SaeAh.

that mf "sword king" is so fucking disgusting like truly he's more terrible than that bitch cause ain't no way THE sword king don't resist even a bit...