After much discussion between Lister, Priscilla, and Anko, they ultimately decided to temporarily suppress the matter between Lister and Priscilla, only spreading a bit of news within Priscilla's castle.
After all, the relationship between monsters and humans was already like fire and water. Lister worried that this news would directly ruin the Demon Lord's Castle that Priscilla had painstakingly built up to accommodate the vast majority of monsters, which was not something he wanted to see.
Later, Lister found an opportunity to slip away while Priscilla and Anko were talking, returning to his own room.
In just one day, he had achieved a great leap from being a guest in the Demon Lord's Castle to the prospective Demon Queen consort. Truly a cause for celebration...
"..."
At this time, night had fallen upon the Demon Lord's Castle. The twin moons on the horizon cast a bleak, clear radiance that shone through the window, illuminating this long corridor.
Lister gazed at the moonlit carpet, his thoughts drifting lightly with the moonlight.
He asked himself... did he truly have feelings for Priscilla deep enough to form a marriage pact?
If he answered yes to himself right now, it would certainly be a lie.
Frankly speaking, putting aside the many years that had passed, even back then, he had never viewed that Crimson Claw as a member of the opposite sex. To suddenly say they would be together now, Lister felt he couldn't deceive his own heart.
He agreed partly due to being pushed into it... after all, there weren't any better options now, right?
He searched his soul and realized his feelings for Priscilla were definitely not as deep as Priscilla's for him.
Realizing this now... Lister felt a bit uncomfortable in his heart.
He was a staunch believer in marriage equality. A marriage with unequal emotional investment was like a crooked tree - the deformity might not be noticeable when it's a sapling, but once it takes root and grows, it becomes irreparable.
Lister took a deep breath, then secretly made a decision in his heart.
Alright.
Starting tomorrow, I'll do things that will make me fall in love with Priscilla.
With this thought, Lister felt slightly more at ease and began striding towards his room.
...
"Hey, sis, are you okay?"
Inside Lister's room, the black-furred Ai wagged her tail, looking at Airu who was leaning on a broom looking drained.
"Ha, ha..."
Airu's face was flushed as she panted nonstop.
She felt a chill in her limbs and a lack of strength. If not for leaning on the broom, she probably would have plopped down on her butt.
"I'm... I'm fine..."
Airu answered with difficulty while slowly standing up with the support of the wall.
"Have to... quickly finish cleaning Lord Lister's room..."
"Sis..."
Just then, the door opened and Lister walked in, looking towards the sisters.
"Lord Lister..."
"Mr. Lister."
Ai immediately wanted to say something, but before she could speak, Lister had already noticed Airu's condition to the side.
He furrowed his brows and strode over, pressing his forehead against Airu's...
So hot.
Although beastkin had higher body temperatures than humans, this clearly exceeded the normal range. A rough estimate put it over 43 degrees Celsius.
At the same time, Lister noticed liquid pooling under Airu's eyelids, her face flushed, breathing shallow and rapid. She blankly stared at Lister, seemingly unable to even speak.
"Airu?"
"Ah... sorry, Lord... Lord Lister, I'll get up right away..."
"No, sit down."
Lister pulled Airu, who was still trying to force herself up, and let her lean against a nearby chair.
"Do as I say next, okay?"
"Mm, mm..."
Lister had Airu sit down, then pressed his hand against the base of her ear.
"Ngh..."
Airu let out a faint muffled groan, but Lister paid it no mind, carefully feeling with his hand.
Similar to humans, beastkin monster girls had lymph nodes of various sizes all over their bodies. These lymph nodes normally couldn't be felt, so being able to palpate them indicated a local infection.
Sure enough, Lister could already feel some swelling at Airu's post-auricular lymph nodes.
"Open your mouth... Ai, did Airu do anything special today or go anywhere unusual?"
Lister gently pried open Airu's mouth while asking Ai beside him.
"...This idiot sister, she went out looking for you this morning with wet hair because she didn't see you in the room. Her hair dried and you came back on your own. Then..."
Ai recalled the time under the Demon Queen's bed and hesitated, but still didn't say it out loud.
"Then she broke out in a cold sweat and has been cleaning the room since coming back..."
"Okay, got it."
Hearing Ai's description, Lister more or less understood.
During university, Lister had already found ways to observe the existence of microorganisms in this world using a self-developed microscope. So common diseases like the current bacterial cold still belonged to the common illnesses of this entire world.
"Airu, move your tongue, don't block there."
"Mm..."
Airu let out a dazed, aggrieved hum, then moved her tongue, revealing her pointed canines and her oral cavity radiating scorching heat.
Having Lord Lister look in here... so embarrassing...
But what Lister was looking at were her tonsils in her throat, which already had visible congestion and swelling.
"Your throat is very uncomfortable, right?"
"Mm-hmm..."
As Lister spoke, he took out a small metal box from somewhere in his clothes. Upon opening it, it was filled with yellow, dewdrop-like spheres.
"Mr. Lister..."
"This is something extracted from the bark of the golden trees in the Elven Forest, with a layer of wax honey sealing the outer skin. It was originally made specifically for children, but I never thought it would still be useful now..."
Lister took out one and placed it in Airu's mouth.
"Eat a candy and the swelling will go down. Be good, swallow it quickly."
"Mm..."
A faint sweetness spread in Airu's mouth. This was an extremely precious sweet flavor that made Airu lose herself for a moment, just wanting to savor it a few more times. But unexpectedly, before long, an overwhelming bitterness exploded on her taste buds. Airu's originally cute smiling face instantly twisted into a knot.
"Do you still remember it, Ai?"
Lister turned his head to look at Ai, smiling as he asked her.
"Mm!"
Ai also excitedly answered. That yellow pellet... was exactly the same as the few she had eaten years ago.
"Today, I can tell you its name."
Lister stood up while handing a glass of water to Airu, who was still being tormented by the bitterness.
"Although the structural composition is slightly different... I still want to call it aspirin."
...