https://www.pixiv.net/en/users/60003921

Google translated
Honkai, that's what humanity calls the calamity from beyond the heavens. Can we win? Will we win? Despite the fear of the unknown that grips people, a group of people have always persevered, carrying the burden. Today, the resistance continues.
"This is the content of our experiment today. Do you understand, Cecilia?"
"I understand, Doctor. This is a choice we must make to defeat the Honkai." The girl called Cecilia looked firmly at the man before her. "I... am prepared."
"Well, let's begin then."
...
"The device is now activated. The physical restraints are because establishing a direct connection between the Divine Key and your body will cause immense stimulation. But once the connection is successfully established, you will gain a tremendous boost in combat power. Please understand this."
"Hoo~~, well, Doctor, let's begin."
"Okay, Little Yellow, activate the device." *Snap!* As the instrument began operating, the Divine Key that had pierced countless Honkai beasts finally aimed at its master.
"Um... Ah~!!... I'm... fine, please continue." The girl responded to the doctor's concerned gaze. But...
"Eh... Ahhh❤! No... Don't look at me... Ohhh... Ahhh...! Ohhh...!" Although everyone present understood this was just a side effect of the experiment, the girl's shame still lingered.
"Put this on. Although it won't lessen the stimulation, it can make your body feel better through mild brainwashing."
"Um... Thank... Doctor... Ohhhh...!"
"...You're welcome. Don't force yourself to speak anymore. This experiment will continue for a long time... Please forgive us incompetent adults."
12 hours later
"Umhhh!!...!... Ohhhh... Ohhh...!...!"
"Doctor! Look at her lower abdomen! The connection to the Divine Key is almost complete!"
"Hey, Cecilia? Can you hear me?" The doctor removed Cecilia's blindfold, revealing her dazed eyes. Despite not knowing if she heard him, the Doctor continued, "The main objective of the experiment has been achieved. Next, we need to convert the Honkai energy introduced into your body from the Divine Key into harmless substances (bodily fluids) and expel it. This process will be stimulating; I hope you can persevere a little longer."
With the Doctor's nod, the equipment resumed operation. Cecilia, still dazed, felt a heat rising in her lower abdomen and her female genitalia rapidly changing.
"Ugh... Ahh... Ohhhhhhh...!...! Ughhhhhh... Ah!...!...!" Frenzied moans, mixed with scattered breast milk and vaginal fluid, filled the laboratory…
"Ah... Ah... Little... Little Yellow?"
"You're awake, Cecilia-chan. The experiment was a success; we've taken another step closer to defeating the Honkai."
"That's great. Then…" Cecilia tried to move her restrained body, though she couldn't make any movement, Little Yellow saw through her thoughts.
“Cecilia-chan, we need to wait a little longer. The conversion rate of your bodily fluids during the expulsion of excess Honkai energy far exceeded our initial plan, so we had to take an emergency halt. We're very sorry, but according to our calculations, you'll need another week to expel the remaining Honkai energy from your body before you can leave. But don't worry, the Doctor has entrusted this entirely to me; this time we'll control the amount expelled.”
“Little Yellow, wait a minute…uhhhh…haa…ohhhhhhh❤…!”
“Hehe, stay by my side, Cecilia-chan.” The person called Little Yellow whispered in a low voice from around the corner of the lab.
Chapter 2
The world asked humanity: "Can humanity defeat the Honkai?"
"Humanity will definitely defeat the Honkai!" the girl holding a baseball bat answered.
This was the only possibility humanity grasped after countless attempts across numerous worlds and thousands of years of trials.
However, today, at least in this world, one man's selfishness destroyed it all. (For background information, please refer to the previous work)
"Impossible!!! How could my theory be wrong!" The man, his expression crazed, frantically scratched his graying hair and roared, "Even Cecilia couldn't defeat a Herrscher, how?! How can we...?"
"Dr. Huang, I know Cecilia is very important to you, but the situation is urgent. Given the current situation, our only remaining option is Z-26..."
"Z-26... Yes, Z-26! Our theory must be correct! It's just... it's just that our previous approaches were too lukewarm! Quickly notify the last S-rank Valkyrie! Begin preparations for the experiment!"
...The last S-rank Valkyrie of Schicksal, with long purple hair and wielding a long sword, known as the Ice Queen of Thunder, was now blushing deeply. She was naked and strapped to a device, and the long sword that had once fought alongside her was now being "held" in a way she had never imagined.
“Dr. Huang… Dr. Huang, I’m ready…” The girl clearly felt her former partner pressing firmly against her most important part as a woman.

“Good! Very good! The specific details have already been explained in the previous notification, so I won’t repeat them here. You! Start the device immediately!” With Dr. Huang’s command, the machine began to operate.
“Eh… Eh eh ah ah ah!… Hmm hmm hmm… Hmm… Hmm…” The naive girl experienced this unfamiliar but intense pleasure for the first time. Even so, her pride as an S-rank Valkyrie compelled her to grit her teeth and endure it. However, even this small act of perseverance was not permitted.
"Activate the brainwashing blindfold, set it to convert all pain into pleasure, and prevent fainting and personality breakdown. We must succeed this time, no matter what!"
"Mmm...oh...oh...oh...ah...mmm...ee...ee...ah...ah...ah..." Accompanied by the low hum of the machine, the girl's moans echoed in the laboratory...
"Dr. Huang! Look at her abdomen! We detected an energy reaction different from Honkai! It's spying on us!"
"Good! Quickly increase the power to solidify the Stigmata!"
"...Ha...No...ah...ah..." The girl's protests were ignored, just like the past dozen hours. In fact, the words of protest turned into helpless moans as soon as they reached her lips. Until those people achieved their desired result, all she could do was endure...
"Hey! Hey! Our experiment was a success! You have gained power far exceeding that of Honkai! Next, we will convert all the excess Honkai energy in your body into bodily fluids and extract it!"