
More Spoilerrrrrrsssssss (a lottt)
So he was tricked by Gioro, the dude who just poisoned Haniel. He thought he was just going to take enough power from the brother to become Pope, but ended up taking enough to kill him. During the ceremony to become the Pope, the new Pope must kill a sacrifice. Gioro again tricks Orias and makes Haniel the sacrifice, so he kills both his childhood friends. The trauma causes him to go a bit crazy and he manipulates his own memory to make him forget what happened.
For further context, the original Haniel and her brother were Pope candidates due to their holy power. If you give someone part of your name, you give them some of your holy power. "Orias" the capture character actually had no name. To let him join her and her brother in the church, Haniel gave him the "El" part of her name and he became "El". As Haniel's original power was memory manipulation, "El" gained that power as well.
Now, the important part to keep in mind is that names allow you to steal holy power. Orias was actually the name of Haniel's brother. When El stole all of Orias' power, he gained the name Orias, gold hair and eyes, and is the capture target we see in the story.
Why did he want the power? "El" was in love with Haniel, and Haniel was in love with Ardal. He wanted power because he believed Ardal's strength was one of the reasons Haniel loved Ardal, and "El" wanted to earn her love. Ofc he went about it the wrong way due to jealousy, but "El" didn't intend for the original Orias and Haniel to die, that was Gioro's scheme to get power.

Oh yeah def. Do keep in mind though that this plot line will be operated under for a while since neither Haniel nor the capture target Orias know the truth. The truth is revealed in the side stories, so literally after the entire main storyline is over.
I'll pull out a direct quote though (Spoilerrrr for anyone who doesn't want to read part of the novel):
"I sorted through the memories that had just surged into my mind.
When I tried to recall information about Orias, the details naturally came to me.
The golden-haired boy standing before me was Orias, Haniel’s older brother.
And just like me, he possessed the same memory manipulation ability that I had just unlocked.
A month ago, my sibling and I had awakened this ability along with our holy power, and the house we were currently living in had been obtained through this ability.
Which meant—the Orias curled up over there wasn’t Haniel’s brother, Orias.
...
But the more I thought about it, the more confusing it became. Based on the memory fragment I had just obtained, the golden-haired boy was clearly Orias, yet the Orias I knew was undeniably the white-haired child."
Lemme correct the spoiler that someone posted.
She isn't his sister. Orias stole her brother's holy power and gained an appearance similar to him, then lost his memory. Technically, Orias and the original Hanel are childhood friends. They are not at all related, so y'all can relax lol