(If a story is to be written, it must be finished. What follows are some things about Otto that Kallen didn't know.
Just consider the parts where Kallen appears as stories she tells Ryn and the others.
The parts with only Otto are things the author wants everyone to know about Otto; Ryn, Kiana, and the others will not know about them.)
————————
Due to the loss of the war, Kallen was stripped of many of her rights, and her reputation plummeted. Her and Otto's positions in Schicksal were completely reversed.
Nearly all the Honkai Beasts were sealed by Kallen in the basement of the Schicksal Cathedral, and the Honkai now spread in the form of a disease.
Kallen saw that Otto had been engrossed in his laboratory recently. She felt that if Otto was already working so hard to save the world, she couldn't fall behind either.
The phantom thief became increasingly rampant, to the point where Schicksal had to dispatch Valkyrie units to capture her. But Otto was desperately protecting Kallen, even replacing Schicksal's Valkyrie units assigned to arrest the phantom thief with a Valkyrie unit he had formed himself.
However, Otto never expected that the loyalty of his Valkyrie squad's captain, Eleanor, to him was borderline fanatical. This led Eleanor to misunderstand Otto's orders and begin relentlessly hunting the phantom thief, Kallen.
————————
After the success of the experiment on Eleanor, Otto became more and more obsessed with human experimentation, even attempting to experiment directly on healthy, living people.
"Becoming a great inventor and saving the world with Kallen" had become almost an obsession for Otto.
Otto realized he seemed to have gone completely astray...
But there was no turning back now. The living, the dead, the undead... Otto didn't know how many he had killed, but he knew he must never let Kallen find out what he had done...
But paper can't wrap up a fire...
————————
The commoner girl from the flower shop—Sasha—awakened a Stigmata. Sasha's abnormality led Schicksal to discover her.
She should have been a good candidate for a Valkyrie... but the Honkai had already taken the form of a plague...
One night, black-clad men from Schicksal broke into Sasha's home and took her away. This scene was witnessed by the phantom thief Kallen, who had just completed her righteous deed.
Kallen tried to stop them, but they fled with Sasha.
She chased the black-clad men to Victor's mansion...
Kallen searched the entire mansion but couldn't find Sasha. However, this time Kallen discovered the basement she hadn't found during her first visit to Victor's mansion...
"What is this door made of?! Why can't even I break it open!" Kallen frantically attacked the iron door of the basement, but it didn't budge. "Why is there a Schicksal symbol on the door..."
"Who's there!? What are you doing? Guards! Someone, quick!"
The commotion Kallen made didn't break open the basement door, but it did lure Victor out.
"If you don't want to die, open this door right now!" Kallen grabbed Victor and slammed him against the door.
Victor couldn't for the life of him understand why the phantom thief, after robbing him of all his money, would pay him another visit. But, fearing for his life, he opened the basement door anyway.
After all, inside were... Otto and the Valkyrie unit.
Hearing Kallen's voice, Otto immediately hid. Otto already understood that what Schicksal was doing in the basement could no longer be hidden from Kallen, but at least... he couldn't let Kallen know that he was also involved...
"Sasha... Why!? Why are there so many little girls locked up in here!!! What is going on!"
Holding Victor hostage, Kallen walked into the basement only to see a heartbreaking scene... Not only was Sasha here, but many other children were also imprisoned.
"Let them go!" Kallen yelled, ordering Victor.
"I can't! These are the Overseer's orders," Victor shouted, struggling. He knew Kallen wouldn't kill him, but if the people were released, Otto and the Overseer would definitely kill him. *Speaking of which, where the hell did that bastard Otto go? Get out here and handle this damned woman!*
"Release them now, or I'll break your arms and legs immediately."
"I can't! This research is extremely important! It will help us cure the Black Death..."
"Nonsense!"
"No... you don't understand." Victor stopped struggling. Since Otto wasn't coming out, he would be the one to tell this naive little girl the truth.
Victor pointed to the Honkai crystal in front of Sasha and said to Kallen: "The Black Death can be cured with medicine, but if we can unlock the secret in that box... we can defeat the Honkai completely!!"
"Captain Kallen!"
"What?"
Hearing someone call her name, Kallen instinctively turned her head to respond, only to see Eleanor looking at her with a Valkyrie unit.
"So it was you, who has obstructed Schicksal time and time again... hindering Lord Otto. No matter your reasons, I must take you back!!" Eleanor, holding three daggers in each hand, lunged at Kallen.
"Eleanor, listen to me! These children are innocent..." Kallen didn't want to harm Eleanor, nor did she want to involve the children, so she kept dodging without fighting back.
"Get serious, fight back!"
Unable to land a single hit on Kallen, Eleanor shouted in frustration.
Then Kallen fought back... and sent her flying with a single kick...
"Stop this... I don't want to fight with you..."
"Hmph, don't underestimate me..." Eleanor reached behind her, then began to activate her Holy Blood. Her hair gradually turned white... and in her hand, a pitch-black long spear began to materialize—Black Abyss.
Black Abyss, a part of the Divine Key Abyss Flower. After the fall of the Schariac family, they not only gave the right to bestow the name of Saintess to the Apocalypse family but also gave Black Abyss, a part of the Abyss Flower that represented the Saintess's identity, to the Apocalypse family.
With her Holy Blood activated and empowered by Black Abyss, Eleanor instantly suppressed Kallen. The withering power released by Black Abyss continuously weakened Kallen, leaving her entire body powerless.
Lacking equipment, Kallen could only dodge continuously this time. But eventually, under the constant debilitating effects of Black Abyss, Eleanor found an opportunity and slashed her leg.
The power of Black Abyss spread upwards from the wound on Kallen's leg, and Kallen sank to her knees, powerless.
"Stop struggling. I won't let you harm Lord Otto again."
Eleanor raised Black Abyss high, preparing to execute Kallen on the spot.
Kallen closed her eyes. Corroded by Black Abyss, she no longer had the strength to resist.
*Drip, drip—*
However, the strike Kallen anticipated never fell.
"Stop it! Eleanor!" Otto had grasped Black Abyss with his hand, and fresh blood dripped continuously from the spear.
"Lord Otto!!"
Seeing Otto appear behind her, wounded by her Black Abyss, Eleanor frantically threw the spear away.
*Why... why is Otto here?!*
But before Kallen could think further, Otto ordered Eleanor not to harm her, then summoned other members of the Valkyrie unit to take Kallen away and imprison her.
Watching Kallen being led away, Eleanor turned to look at her Lord Otto.
"Is your hand alright... Lo... Lord Otto!!"
Having been cut by Black Abyss, Otto had lost blood and been corroded by the withering power. He had already fainted...