"So Kars and Sister have been sharing this little secret too. No wonder she kept me from cuddling him to sleep; it was all for this!"
Flandre didn't consider asking Kars if this was true. She remembered their earlier conversations and knew Kars wouldn't tell her anything about this kind of thing, even if she asked. But compared to her own discreet activities with Kars, she figured her sister's secret would be easy to uncover. After all, they were right here beside her; it would be simple to find out what was going on, unlike her and Kars, who always had to hide away.
Flandre's mood instantly brightened, and a smile spread across her face. Remilia, sitting nearby, sighed slightly at Flandre's sudden happiness.
"The atmosphere in the Scarlet Devil Mansion is truly getting weirder," Remilia mused. Ever since Kars arrived, the previously normal mansion had begun to veer in strange directions, and she couldn't stop it, since she herself was part of the problem. Only Hong Meiling and Sakuya seemed unaffected so far. Everyone else had their own issues, with Koakuma, herself, and Patchouli likely being the most serious cases.
Remilia sighed softly at the thought.
"Little Auntie, I'm back! Huh? Little Auntie Remilia, what's wrong?" Kars, seeing Remilia sighing right as he returned, immediately asked what was wrong and why she looked so distraught. Had something happened at home?!
"Nothing, I was just pondering some things." Remilia shook her head. Kars, seeing her dismiss it, didn't ask further. Flandre then grabbed him, demanding they go play, and as time slowly passed, the action they were waiting for began.
Inside the bedroom, Flandre didn't go to sleep immediately. She lay still, waiting to see what her sister would do with Kars. Pretending to sleep was exhausting, and she had to fight off her exhaustion. Eventually, she chose to bury her face in Kars's back, making it harder for anyone to tell she was awake. Flandre waited quietly until she was almost drifting off before finally hearing a slight noise. Soon, she saw Kars's hand start to move, seemingly doing something. "They really do wait until I fall asleep to sneak in their activities," she confirmed.
After Flandre confirmed it, she heard a very familiar sound—the same wet, kissing sound she and Kars made when they secretly kissed. Flandre's cheeks instantly puffed up in anger. Her sister forbade her and Kars from doing this, saying it was inappropriate, yet she was doing the exact same thing herself! "Sister is a big liar!"
Thinking this, Flandre angrily got up, wanting to properly question her sister about why she lied. She immediately turned to face them, and Remilia's expression instantly turned to one of shock.
"F-Flandre?! When did you wake up?"
Being caught red-handed by Flandre made Remilia panic. Facing her sister's glare, Remilia felt utterly humiliated by the situation. "Sister! You told Flandre that kissing Kars was wrong, but you're doing the exact same thing with Kars?"
Faced with Flandre's accusation, Remilia couldn't answer immediately. Her mind was racing, unable to come up with any reasonable explanation for the situation. "I… I'm actually…" Blame Kars? That clearly won't work! She was wide awake, but Kars had been sleeping the whole time. Flandre would never believe that.
While Remilia was in a state of confusion, Kars bit her breast. Seeing this, Flandre's eyes widened slightly. She instantly understood what her sister had meant when she talked about Kars biting her chest. So that's what happened. "Don't look at that, Flandre!"
Remilia covered her face. Having this happen right in front of Flandre made her feel incredibly ashamed. One hand shielded her face while the other weakly pushed Kars, trying to make him stop. Finally, Flandre, unable to watch her sister look so close to tears, pulled Kars away, freeing Remilia.
"Well, that's what happened…" After some explanation, Remilia described the situation between her and Kars. At this point, there was no longer any need to hide it, so she told Flandre everything.
"Hmph! Sister, what you did was really unfair. Not only did you do the very thing you said was wrong, but you kept it a secret from Kars too!"
"H-How could I let Kars know about this kind of thing?!" Remilia said, blushing fiercely. If Kars knew, wouldn't that be even more embarrassing? As it was, her actions felt shameful enough. How could she let Kars know she was doing something she told him was forbidden, making her a blatant hypocrite? Where would her Little Auntie pride go then?
"Then you have no reason to stop Flandre anymore, do you, Sister?" After all, the original excuse was completely invalid now.
"...Ah! Fine! You can kiss Kars. Is that enough? But… you absolutely must not tell Kars, understood?" Remilia wasn't ready for that. She just wanted to continue her secret activities; she wasn't ready to tell Kars about it.
"Mhm! Flandre understands!" Flandre laughed. This unexpected outcome granted her exactly what she wanted.
Then, under Remilia's conflicted gaze, Flandre leaned down and kissed Kars, doing the same thing Remilia had just done. "Hey, Flandre wants to try that too. It looked like Sister was having a really good time just now."
Flandre lifted her own nightgown, pressing her similarly small, flat chest towards Kars. Remilia opened her mouth, wanting to say something, but ultimately gave up. What could she possibly say now?