Disclaimer: I do not own Fairy Tail, or any of its associated characters and lore. That right belongs to Hiro Mashima.
The Moonlit Fire Dragon King
Selene's Temple, Black Moon Mountain, Elentir, September, X792
Using her Moon Dragon Slayer Magic to observe events in Earth Land as well as in the Rift in Space and Time while she and her three Moonlit Beauty Gods bathed in her Elentir hot spring, Selene of the Five Dragon Gods grew increasingly impressed with how the seven Dragon Slayers, most of which were raised up by Dragons from her own time, were taking the fight to Acnologia as their fellow Earth Landers aided them off their battleground. And judging by the reactions of her henchwomen, Youko, Hakune, and Mimi, they were just as entertained by the Dragon Slayers as Selene herself was.
Upon witnessing the pink-haired adopted son of Igneel and brother of Ignia landing the finishing blow on Acnologia, Selene had made her decision on making things more interesting in Elentir. Turning to the Beauty Gods, she said. "I've decided to bring the Fire Dragon Slayer here, ladies." Licking the lips of her Human form, she added. "He should be quite entertaining. Any objections?"
"Not at all, Lady Selene." Youko replied with a bowing of her head.
Hakune giggled as she commented. "He is quite the looker."
Mimi turned to the image of the victorious Dragon Slayer, Natsu Dragneel, with a stoic, yet blushing, face. "I am curious how his strength would be like against mine."
"Then it's settled." Selene said with a sly smile for the sake of argument, even though she would have done it with or without her subordinates' agreement.
With the Magic of Aqua Aera at her disposal, Selene then used the hot spring water as a medium to transport Natsu from the Rift to the hot spring itself just when he and his fellow Dragon Slayers were automatically being returned to Earth Land at that moment. Upon arriving, Natsu looked incredibly surprised.
"Huh? Where am I? Where's everyone else?" Upon noticing the rather nude four women that he was in the hot spring with, he then said flatly with a barely noticeable blush. "Why aren't you ladies wearing towels in a hot spring?"
Hearing how he said his last question, which surprisingly went in hand with his facial expression, Selene and the Beauty Gods burst into laughter much to Natsu's confused annoyance.
"Will you people take me seriously here already?!" He could not help but shout a demand in frustration, which, much to his own ire, only aroused even further laughter.
Regaining calm first, Mimi told the new arrival. "Apologies, Fire Dragon Slayer, but the way you were asking was funny. To answer your questions, however, Lady Selene summoned you to the world of Elentir while your friends were returned to the separate world of Earth Land. As for the lack of clothing, well, we are bathing, after all."
"You don't mind looking at each other naked?" Natsu asked on instinct before shaking his head and saying. "Never mind that. Why was I brought here?"
Selene then interjected theatrically. "Why for my entertainment, of course, little Dragon!"
"Excuse me?" Natsu said back with a drop of sweat on his head.
"Oh, don't worry, handsome." Hakune said to him flirtatiously. "I'm sure it won't be too troublesome for one of your strength, good looks, and unlimited potential."
"But enough about that." Youko then said while winking at Natsu. "Come join us properly before we get started."
Thinking it over, Natsu ultimately shrugged and began to strip. "Can I at least ask how long I'm going to be here? I have a lot of friends to catch up with just as I'm tired from beating Acnologia."
"Your departure will be at my discretion, Natsu Dragneel, and no sooner." Selene said sharply as Natsu submerged himself into the spring water opposite her and the Beauty Gods. In a gentler tone, she then added. "Still, you should feel honored as much as I am close to grateful to you. Acnologia would've potentially threatened the other Dragon Gods if he seized control of the Rift, so your slaying of him has saved all of Earth Land and still leaves me liable to return to it whenever I please."
"Dragon Gods?" Natsu repeated intrigued. "Since when were Dragons and Gods the same thing?"
Selene chuckled haughtily as she then proceeded to explain. "It's quite the tale, Natsu, so allow me to set the scene." Before she could begin, though, Selene then had a thought that resulted in a devious smirk on her face which brought a shiver down Natsu's spine. "But how about we get better accustomed to each other first?" Standing up, she then laid herself down in the lap of a shocked Mimi.
"Lady Selene!" The taller, more muscular woman exclaimed with a blushing face. "This is too sexy!"
"It's about to get even sexier, Mimi." Selene told her with a conspiratorial wink before then calling out. "Hakune, join me at my right as Youko comes to my left and Natsu is seated in my own lap."
"Okay, if you say so." Natsu obeyed for the sake of argument while the other two women slowly followed their instructions with a blush. Once they were all positioned, Natsu shrugged as he commented. "Well, at least I know all your names."
His hostesses all giggled and then Selene gave a nod to Hakune to act first.
Excited, the latter brought Natsu's face directly to hers and spoke to him. "That is right, Natsu. You may call me Hakune of the Snow, Moon, and Flowers." To Natsu's surprise, she then kissed him. Hearing Youko clear her throat, however, brought Hakune to break off the kiss with a visible pout.
As Natsu stood still trying to process what happened, Youko then copied her fellow underling's prior actions as she introduced herself. "And I am Youko of the Parade of One-Hundred Demons. I believe we'll get along quite well, Natsu."
Her kiss with Natsu soon broke apart when Mimi then grabbed the Dragon Slayer by the neck and stared at him face to face. "I shall be addressed as your Princess, Mimi the Immovable!" She exclaimed before heatedly kissing him on the lips. Savoring the locking of their lips for a good quarter of a minute, Mimi then laid Natsu back into Selene's lap, who stared at him with ecstatic eyes.
"Now that you have met my Moonlit Beauty Gods, Natsu Dragneel, you will know me as the Moon Dragon God." She informed him while licking her lips.
The last part of Selene's sentence had brought Natsu to look stupefied as he attempted to say. "You're a Drag-?!" But was interjected with Selene's turn to kiss him, and it was at that time, that Natsu kissed back as it felt natural to him then.
I originally wanted to pair off Natsu with one of the three Moonlit Beauty Gods per one-shot by having him, Gray Fullbuster, and Happy confront Hakune differently in her case while switching places with their female teammates from the abandoned village Erza Scarlet, Wendy Marvell, and Carla encountered Youko to the forest Lucy Heartfilia and her Celestial Spirits (Taurus, Aries, Scorpio, and Capricorn) confronted Mimi in the other two cases, but then I remembered that those three had the advantage with their Spiritual Arts which would make Natsu earning their affection through fighting a bit unrealistic when you think about it, so I decided to make it so Natsu could meet Selene and her subordinates early under the right circumstances.