Yorihime stayed in the water, pretending not to notice, but her senses were dialed into every muffled moan and wet splash.
Toyohime tried to stay quiet, but she was finding it harder and harder to resist. Having sex right next to her sister was a thrill she hadn't expected to enjoy so much.
"Mmm~ why did you go over to Yorihime just now? And show her your meat?"
"Because she looked like she wanted to see it. I just wanted to give her a better look."
"Eh!? Mmm~"
Toyohime gasped as Kars thrust deeper. Yorihime's body shuddered; she ducked lower into the water until only her eyes were visible.
"Actually, Yorihime-nee knows about us. I've felt her watching us for a while. It's impossible not to notice. I think she's just shy, but she wants to see. That's why she doesn't say anything."
"Aaah! She... she knows?"
Toyohime stared at Yorihime and caught her sister's eyes peeking over the water. The secret was out. Realizing her sister had seen everything and was still watching, Toyohime finally snapped. She stopped holding back.
"Aah-oh! So good! Give me more! More pleasure, Kars!"
Toyohime screamed as Kars hammered into her vagina. The sheer intensity of the scene made Yorihime bolt. She scrambled out of the water and ran back to her room, but the image of her sister's blissful, depraved smile was burned into her mind.
Back in her bedroom, Yorihime tossed and turned. Her head was full of Kars's cock and her sister's face. Her body was burning.
Just as she reached down to touch her pussy, the door opened. She quickly pulled her hand back and closed her eyes, pretending to be asleep. She listened to the footsteps and waited for the sound of more sex. Suddenly, her blanket was pulled back. A body slid in behind her, and hands began to knead her breasts.
"Mmm~ wait! What are you doing, Kars!?"
She knew it was him. She turned to look at him, shocked he would come to her.
"Because you want it too, don't you, Big Sister? Watching us has made your body so frustrated."
"E-even so, you shouldn't be here. You should be with Sister..."
"Toyohime is exhausted. I made sure she was fast asleep before I came to see you. We won't disturb her."
Yorihime looked at her sister's bed and saw Toyohime sleeping soundly with a smile on her face.
"But even so..."
"Toyohime won't mind. She doesn't care if I be with you. She wants you to feel this pleasure too."
Kars pressed his cock against Yorihime's butt. Her muscles tensed at the contact, then slowly relaxed as he began to rub against her.
"You don't hate this, do you?"
Kars kneaded her breasts and nipples until her breathing became heavy. When his hand slid down to her pussy, she tried to grab his arm, but her grip quickly failed. She opened her legs, letting him slide his fingers deep inside.
She couldn't stop herself. She was filled with excitement and anticipation.
Both sisters, sleeping with the same "child"... she couldn't believe it. Especially since this child was with his own mother...
"By the way, Eirin isn't my mother. I'm the 'husband' she told you about. She just thought the 'mother-son' roleplay would be fun during sex."
Yorihime's eyes nearly popped out of her head. Before she could process the truth, Kars's fingers drove her into a screaming, squirting climax.