This is my first story and I'm taking a huge risk by typing something M/MA rated, please tell me what I did right and what I did wrong for the few people that might possibly read this. Keep in mind that whatever they say or think is all in Japanese, just a heads up.
It was a still night, everything was quiet, not to mention the cold, Nepgear opened the sliding door and was greeted by the sight of the bath, steam floating outwards to the sky, she went towards the showers to shower herself before entering the bath as stated by rules, this Onsen was near the edge of Planeptune and was a great place to relax after a day's work, as she finished showering she slowly entered the bath, it was warm to the touch as she slowly sat down on the base of the bath, a huge grin appeared on her face as she began to relax and think about things.
It has been a while since coming back from the Ultradimension and it was there Neptune declared her love for her sister, though it may seem like sibling love, to Nepgear and to an extent Plutia, who was there at the time, thought of it more of like an incestual sibling confession rather than one of normal sibling love, Nepgear blushed at the thought as seemingly impossible situations concocted in her head, in her train of thought, the door opened and standing by it was Neptune who had came later due to some... Matters of importance, Nepgear turned around blushing heavily still with the thoughts she had and managed to let out a "You're finally here Onee-chan." "Yep yep! I'm here alright, now for some nice relaxing bath time." Neptune responded while heading to the shower, Nepgear watched as her sister walked towards the shower area, her small chest taking small hops and the way her sister's lips looked, she began to ponder how they would feel like, "No no no. I can't do that! What if..." She tried to correct her thinking but it strayed away from it.
Soon Neptune entered the bath and sat beside Nepgear, "You've been here for quite awhile now haven't you Nep Jr.?" Neptune asked, "Y..yeah, I have..." Nepgear responded blushing but was covered by the steam, "Ah~ at times like this it sure is nice to relax and enjoy this warmth dontcha think?" "Yeah..." After that they sat there silent for awhile before, "Onee-chan?" "Hm? What is it?" Nepgear started twitching around, getting more embarrassed, "Uhm... Please prove your love to me!" Nepgear nervously shouted, "Hm? What cha mean?" "You did say in the other dimension that you wanted more of me... Soo... I want to make sure you're not lying..." Nepgear replied, "Oh so that's it huh? Well that's easy I'll just..." Neptune moved closer and gave Nepgear a peck on her cheek, Nepgear jumped a bit before asking, "C...can we do it more?" "Why sure, but whe-" Neptune did not get to finish her sentence as Nepgear planted her lips onto hers, Neptune's eyes widened before closing and enjoying the kiss, they broke off for air, "My... That was... Sudden." "I love you Onee-chan... I really do..." "I know that, I love you too my little sister." saying that Neptune pulled her in for another kiss but it was longer, they both circled their tongues around each other, feeling it in each other's mouths, Neptune slowly reached out for Nepgear's left breast and started groping it while Nepgear's hand moved down to her sister's lady part, as Nepgear inserted her fingers in Neptune arched her back at the electricity that was sent, Nepgear feeling around down there was feeling way too good and she was on the verge of cumming, as Nepgear went faster she felt the walls clench her fingers tighter, and soon Neptune came in a very seductive moan, she rested her head on Nepgear's shoulder and said, "It's not nice when you're having all the fun Nepgear..." and raised Nepgear's right leg up high. "Ehhh?" Nepgear shrieked, "This time, we enjoy it together..." with a smug look on her face she pressed both their vaginas to each other, the pleasure was incredible as Neptune began moving, Neptune leaned forward to nibble on Nepgear's left boob while groping her right with her spare hand, the amount of pleasure was electrifying as both sisters were close to the climax. "Onee-chan! I'm... Gonna Cum!" "Me too! Come on! We do it together!" as their breathing got faster and the moans got louder they came and their combined moan resonated through the air, they looked at each other with a smile of their face. "I proved my love for you Nep Jr." "You did... I'm so happy..." tears of joy began to flow as they pulled in for one final kiss.
"Woahoho! Neppy and Neppy Jr. went and done it didn't they? I'm so happy for them, incestual confessions are just great." off behind the fence, a trembling Plutia was watching and schlicking to the events that transpired. "I can't really let them know I was here and spying on them... Teehee, ahh I wish I had a sister." Plutia commented as she slowly got back up and walked away before transforming and flying towards the Planeptune Basilicom.
The next morning back at the Basilicom, the two sisters were holding hands and walked out of Neptune's room, they had another round in there and both were very happy. "Hm? What's with the holding of hands Neptune?" Histoire, vigilant as ever, spotted the two holding hands, "Oh! Uhh It's nothing! Nothing really..." both sisters said in unison as they hid their hands behing their back. "Well whatever it is Plutia came by last night through the world connecting portal." Histy calmly said in a professional tone of voice, "Oo! Where is she now?" Neptune delightfully asked, "She's at the balcony waiting for you." "Alright Nep Jr.! Lets go!" "Yeah!"
Little did they know that Plutia already knows their little secret, but she won't tell them she knows will she? Of course! With how this thing is going I doubt it. The trio went out to play after meeting up leaving poor little Histy to do the work again, but it was all worth it right? After all, this is only the beginning for the two love sisters.