Disclaimer: I do not own Fairy Tail, or any of its associated characters and lore. That right belongs to Hiro Mashima.
The Fire Dragon and the Wet Woman
Onigatsuki, Black Moon Mountain, Elentir, X793
Upon finding himself at the mountain's bottom layer, and separated from his friends, Natsu Dragneel of Fairy Tail took his time fighting through the local Yokai with the intention of taking the fight back to the Moon Dragon God, Selene, and her trio of Moonlit Beauty Gods. However, he was not expecting to see his close teammate, Lucy Heartfilia, reappear to him in the form of a snake-like Yokai herself, a Nure-Onna as Selene telepathically explained, and that both he and Gray Fullbuster would have to deal with Yokai versions of Erza Scarlet, Wendy Marvell, and their Exceed companions, Happy and Carla, in addition to Lucy.
Upon being let out from the tight embrace that the Nure-Onna Lucy was giving him, which was even more enticing as she only had her long hair to cover her breasts, Natsu got himself in a fighting position to hopefully and literally beat some sense into her, but then, after looking at Lucy's form again, had a different idea to really spice things up.
"All right, Snake-Lucy!" He exclaimed in excitement before making his way to her. "Here I come!"
"Don't underestimate me, Natsu!" Lucy responded in her possessed state.
"Fire Dragon's Iron Fist!" The Fire Dragon Slayer shouted as he punched a great fist of fire into the ground near Lucy, who only moved away in a confused type of reaction as she did not expect him to punch nowhere near her on purpose.
Before the transformed Fairy Tail Wizard could think of what Natsu had in mind, however, she was surprised when the normally boisterous Dragon Slayer grabbed hold of her upper body, turned Lucy's head towards his direction, and planted his lips on her own in addition to inserting his tongue in her mouth in a steamy kiss.
One which the shocked Lucy, in her controlled phase, attempted to fight back, only to slowly return it.
Observing the make-out between the Human son of Igneel as well as the newest Nure-Onna to Black Moon Mountain's bottom habitat through Magical means, Selene and her underlings all had varying, yet similar, reactions to the scene occurring in Onigatsuki.
"My, my." Selene let out with a blissful smirk in her Human form while most of the gathered women gossiped in awe. "The young Dragon Slayer certainly can be passionate when he wants to be."
"Damn, that's just so sexy!" The muscular giantess of the Beauty Gods, Mimi, commented in an excited, yet restrained, way. "It's like he's on the path to claiming her for real!"
The Beauty God who captured Natsu, Hakune, hummed in slight envy. "I feel jealous of her just looking at this."
"That does look nice." Youko, the Beauty God responsible for the Yokai transformations, admitted with a small blush before she then thought of something and began to panic. "Wait! No way! I feel my control over her fading due to her feelings for him!"
Before the other partygoers could respond to that development, they saw Lucy and Natsu breaking apart from their kiss with the latter asking the former. "You back to yourself on the inside, right?"
Nodding, Lucy replied. "Yeah, I'm okay, but before we go look for the others, I have an idea to get help from an old friend."
Slithering back from Natsu, the blonde Wizard then used the Spiritual Power she had as a Nure-Onna to conjure up a small lake in the cavern with Water Magic. Once done, she then exclaimed aloud. "Aquarius, come forth and aid us!"
While the Fire Dragon Slayer had a confused expression and Mimi was reminded to inform her comrades about something, a blue-haired Mermaid appeared from the lake with a smirk in both Fairy Tail Wizards' direction.
"It's been a long time, Lucy and Natsu." Said the Mermaid before speeding around Lucy's behind and harshly spanking where her Human rear end would be at, which had the side affect of returning her to Human form.
"Was that necessary?!" Lucy could not help but shout annoyed.
"You're welcome, brat." Aquarius said back flatly before turning to Natsu with a comeback smirk. "I saw the way you handled her as a wet woman, kid. Very nice. Reminded me of my time with Scorpio."
Shrugging with a grin, the Dragon Slayer said in justification. "Felt like a good idea at the time." Then turning his around back and forth, he then said with a fight-crazed smile. "I hope you and your women are ready, Selene, because I'm coming for all of you next!"
Many of the female attendants as well as Mimi and Hakune could not help but heat up at the thought of that while Youko, having previously been frustrating from her own Spiritual Arts being overturned from a kiss and a surprise newcomer, tried to divert her eyes from Natsu's wild look as did the remaining attendants.
Selene, on the other hand, chuckled eagerly. "Probably not what he meant, but even I'm getting curious on what he tastes like."
"Really, Natsu?" Lucy asked back to teammate with dry tone of voice.
Sweating from how it sounded like, Natsu said awkwardly. "That's not what I meant, Lucy! At least not entirely!"
Aquarius scoffed as she and Lucy began to walk away. "Not entirely, he says."
Natsu was having none of it. "Hey, Selene was naked when I saw her, and all her women were acting like female versions of Gramps! It's not my fault that a lot of them were nice to look at!"
With respect to those who may have taken the current arc in 100 Years Quest a little too seriously and acted prematurely as a result, I like to think what I depicted as well as what Chapter 75 presented are better than anything angsty, or Natsu being overly reluctant at fighting a possessed Lucy. Granted, I honestly thought about making it a lemon, considering how Lucy looked and acted as she was, but decided against it to keep it simple.
I also know that I may be a bit biased in favor of Selene and her followers being later presented as reasonable simply because she, Hakune, Youko, and Mimi (the last three need to be added to FanFictionNet's character selection, by the way) are nice to look at in their own distinct ways, but we will see how the arc goes down before I write about those four female characters being paired with Natsu. All the same, I admit that everyone has different stimuli, though, so take what you will.