AN: Thank you Wadeparker, Goku275, NinjaFang1331, cg037, kratos1991, AliceCullen3, scoolharis, and InstinctMW.
kratos1991, the promise was only to keep Natsu and Millianna's relationship a secret until it was too late for Erza ditch the S-Class Trial and hunt down/possibly castrate Natsu. As for defeating Tartaros, Sabertooth's top members were shown to be similar in strength to post-training/2nd Origin Fairy Tail. When combined with a Natsu whose seven years stronger, assistance from Ultear and Meredy (two very powerful mages), and Tartaros lacking Demon Minerva and Demon Jiemma, I felt that a victory was at least possible.
That's just me, though. Anyway, enjoy the chapter!
"Seven years!?" shouted Lucy, Gray, Erza, Wendy, Carla, Juvia, Gajeel, Levy, Lily, Cana, Mirajane, Elfman, Lisanna, Freed, Bickslow, Evergreen, Laxus, Gildarts, and Makarov.
"Yeah, and a lot has happened in that time," said Max. "For starters, most people left the guild. Not counting you guys, we have less than thirty members."
The Tenrou group grew somber. So many of their comrades had left.
"I can't really blame them, though," commented Makarov, to the others' surprise. "With all of the upper echelon suddenly gone, it's a miracle that Fairy Tail didn't fall apart completely."
"We almost did," said Alzack. "The number of jobs we were receiving plummeted, to the point where we lost the guild hall and had to buy a small building on the outskirts of town."
"What happened?" asked Erza.
"Ironically, we were saved by a Guild War," continued Bisca. "We ended up crushing a new guild called Sabertooth, who had gained a big reputation. Not only that, their five strongest members ended up joining Fairy Tail. Business really started picking up after that. Although, we've only gotten three new members since then, one of whom is Romeo."
"How nice for him," said Mirajane cheerfully. "I can't wait to meet our guild's new members and see the new guild hall."
The six rescuers shared an awkward glance, then Warren spoke in an uncomfortable tone. "Actually… the new guild hall got demolished about a week ago and we ended up buying back the old guild hall."
"What, did Natsu accidentally roast the place?" joked Gray. "Is that why he isn't here? Embarrassment?"
"Gray, your clothes," pointed out Cana, causing him to go 'Aah!' "Although, now that you mention it, where is Natsu?"
"Yeah," agreed Lucy. "I know that he hates vehicles, but there's no way that would stop him from reuniting with us as soon as possible. What happened a week ago?"
"Well, you see…" began Jet uneasily. He sucked in a breath, then blurted out everything. "Tartaros went on a rampage, wiping out the Magic Council to steal a magic-destroying bomb called Face. They did this to resurrect their leader, an Etherious called E.N.D., because all of them were also Etherious, demons created by Zeref. They attacked Fairy Tail because apparently E.N.D. was dormant inside of Natsu and could be awakened through Natsu's negative emotions. Luckily, we were able to narrowly defeat them and stop Face from erasing all the magic in Fiore."
"…" the Tenrou Group could only respond to this with stunned silence. Not only had they just (from their perspective) defeated Grimoire Heart, apparently the rest of their guild had recently stopped Tartaros.
"Wait…" started Wendy, growing scared. "…but if Natsu was E.N.D., does that mean that he…"
Everyone's expressions became grim, filled with concern for their hot-headed friend. Was Natsu dead? Or, worse, was he no longer Natsu!?
"No!" exclaimed Droy, realizing the misunderstanding and desperate to stop it. "Natsu's alive! He burned E.N.D. out of himself and thrashed the Dark Guild's de facto leader! He's just busy dealing with his guild master duties, reporting what happened to the authorities, and reorganizing Fairy Tail after what happened!"
"Natsu's guild master!?" screamed the Tenrou group, even more surprised than when they discovered that seven years had passed.
"How has the guild not been run into the ground with Salamander in charge!?" shouted Gajeel, before freezing in horror. "Wait a second, does that mean he's our boss now!?"
"As the only remaining S-Class candidate, Natsu was the best option," explained Warren. "Besides, all of the actual work is handled by Macao and Wakaba, who have become his advisors. Natsu's basically just a figurehead."
Everyone sighed in relief. A nightmare had been averted.
"Speaking of Natsu," spoke Erza, irritation entering her voice and scaring the rescue team. "I heard right before the S-Class Trial that he had been dating my friend, Millianna. Would any of you know how their relationship has gone?"
"It's funny you should mention that," said Bisca nervously. "The two of them got married just after the S-Class Trial, and now they have two kids."
"NATSU'S MARRIED/A FATHER/HAS KIDS!?" cried the Tenrou group, even more surprised than when they discovered that Natsu was guild master.
The rescue group sighed, exasperated. This was going to be a long trip.
"We're back!" declared Lucy happily as she and the others entered the recently reacquired guild hall. They all looked around the place, taking in how much different things were after seven years.
"Aside from the lack of people, it hasn't changed one bit," observed Freed, noting that only a handful of people were currently present.
Said people noticed the new arrivals and came over.
"Welcome back!" exclaimed Romeo.
"You're really here!" shouted Laki and Kinana joyfully.
"It's good to see all of you again," greeted Reedus.
"So, you guys are the lost members," spoke Orga, cracking a knuckle. "I'd like to see what you can do."
"You forgot to tell them your name, Orga," critiqued Rufus, before turning to the Tenrou group. "My name is Rufus Lore. It's a pleasure to meet you, one I'll definitely remember."
As the Tenrou group introduced themselves to Orga and Rufus, two more mages arrived.
"It seems the mission was a success," noted Minerva, scanning the group. "You can call me Minerva. I'm Fairy Tail's most recent S-Class Mage."
As the Tenrou Group heard that the guild had apparently promoted several S-Class Mages while they were gone, their reactions varied from surprise to irritation to excitement.
"'Most recent'?" asked Gildarts, raising an eyebrow. "How many others are there?"
"Two, though Sting and Rogue are on an S-Class mission right now," answered Yukino. "I'm Yukino Agria, by the way. Nice to meet all of you."
"It's our pleasure," replied Makarov politely. "I must ask, though… would you happen to know where Natsu is?"
"He's at a meeting with the newly-reformed Magic Council, giving a report on the Tartaros incident," explained Minerva. "Him, Wakaba, and Macao won't be back until later."
"I see," said Makarov. "If that's the case, then there's nothing we can do but wait."
As they waited for Natsu's (and, in Erza's case, Millianna's) return, the older members of Fairy Tail bonded with the newer members.
Lucy, Levy, and Yukino talked about a number of subjects, most notably Celestial Spirits and the fact that they collective possessed every gold key. Minerva chatted with Erza and Mirajane about their respective S-Class Trials, not to mention shared with them the various ways that Blaze was adorable. Rufus, Gray, and Elfman exchanged stories of their recent fights with the Balam Alliance. Orga and Gajeel argue about who was stronger, which turned into a sing-off before devolving into a friendly duet that made everybody else's ears bleed.
Most importantly, Doranbolt show up and Makarov restored his true memories. Everyone's reactions ranged from surprise to amusement upon learning that Doranbolt, the Magic Councilor who used memory-manipulating magic to infiltrate Fairy Tail under the name Mest, was actually a Fairy Tail mage named Mest who manipulated his own memories to spy on the Magic Council.
And, after two hours passed and many friendships were formed, Natsu finally showed up.
"It's finally time," said Natsu, nervous and excited. Before him stood the original guild hall, full of friends he hadn't seen in seven years. Beside him stood his wife, kids, best friend (Happy), and advisors.
He took a deep breath to calm himself, then felt Millianna clutch his right hand and Blaze grab his left. Together, the Dragneels entered the guild hall.
"Hey everyone!" greeted Natsu, grinning broadly. "It took you long enough!"
The entire Tenrou group stared at him and his family in stunned silence.
"Why are you all staring at me like that?" asked Natsu. "Do I really look that different?"
"It's not that," started Wendy, trying to think of a way to break it to him delicately. "It's just that, even though the others told us…"
"None of us believed that a hotheaded idiot like you could become a family man," finished Gajeel harshly. The others winced at the dragon slayer's bluntness.
"Hey!" yelled Natsu. "I'll have you know that I've matured a lot in the past seven years! In fact, now I almost never cause enough property damage during a Job to get the reward taken away!"
"Yeah, because we forced you to do the paperwork whenever that happened," interjected Macao.
"Ugh!" Natsu flinched, embarrassed. "W-well, I actually do the paperwork instead of burning it up, don't I?"
"Pfft!"
"Heh!"
"Hahaha!"
Everybody present started laughing at Natsu, who was clearly still the same person at heart that he was seven years ago. The dragon himself joined in, happy to finally have all of his friends back.
Once the laughter died down, conversations started up again. The Tenrou group was shocked to learn that Natsu was now a dragon, though they quickly recovered and joked about how he was always more beast than human. Wendy got a bit nervous about the thought of becoming a dragon too, until it was pointed out that Natsu only became one because he chose to (albeit unknowingly) in order to fight off E.N.D.'s influence.
Blaze tried to challenge Erza to a duel, only for the S-Class Mage to pick her up and coo over how adorable her namesake was. The other girls joined in, pulling Iggy into their doting.
Gray, Elfman, and Gajeel decided to fight Natsu (allegedly for old times' sake) only to find themselves defeated in a single move, like Laxus had done to the fire mage in the past. This caught the eye of Gildarts, who agreed to a match in the near future. Then, Gildarts revealed to Natsu that Cana was his daughter and the two bonded over being fathers. (Fortunately for the kids, they did not notice the embarrassing conversation.)
The Exceeds also caught up, with Happy showing off his transformation and Musica Sword to Carla and Lily. Happy and Lily also agreed to spar one another, causing Carla to sigh and mutter a line about meatheads.
This carried on for a while, but eventually everyone had to return home. However, as Gray started to leave, Natsu stopped the ice mage and pulled him aside. Then, they had a private conversation about ice, devils, and family.
A week later, once everyone from the Tenrou group had adjusted to the changes (including Lucy grieving her father's death) and reconnected with their now-older friends, Natsu made an important announcement.
"Listen up!" declared the guild master. "I have two things to say. First off, I'm reinstating Laxus as a member of Fairy Tail!"
This earned cheers, especially from the Thunder God Tribe. Makarov was unhappy, but begrudgingly accepted the guild master's decision.
"Second," continued Natsu. "I name Gramps… err… Makarov Dreyar as the fifth guild master of Fairy Tail!"
The guild responded with a mixture of surprise and amusement. After recovering from his shock, though, Makarov asked Natsu a question.
"Natsu, are you trying to return things to how they were seven years ago? Because that isn't necessary. I'm okay with you being guild master instead of me."
"Nah, I just don't want to be guild master anymore," replied Natsu instantly. "I mean, I have to deal with a bunch of boring paperwork and meetings, and I can't go on any Jobs that keep me away from Magnolia Town for too long. Being guild master sucks! I want to go on adventures with my friends and family, not sit in a dumb office all day!"
Everyone laughed at the dragon's rant, even Makarov. Natsu was not, and would never be, a person who just sat back and watched as other people acted.
When their merriment died down, the dragon made one last statement. "Another thing. Now that everyone is back, Millianna and I are finally going to have a proper wedding! It'll be in two weeks, and all of you are invited!"
The entire guild cheered, pleased for the couple.
Shortly after the meeting, Makarov asked to speak with Natsu privately. The newly-reinstated guild master guided the dragon down a hidden staircase.
"You aren't planned to get back at me for dumping the guild master position on you, are you?" asked Natsu, slightly nervous.
"Of course not," replied Makarov, chuckling. "I know better than anyone the burdens of being guild master. The job isn't for everyone, and I'm proud of you for sticking it out these past seven years just to keep Fairy Tail alive. In fact, I believe that, as a former guild master, you deserve to know Fairy Tail's biggest secret."
The two approached a large door sealed with magic. Makarov performed several gestures, causing the magic to dissipate and the door to open. Natsu gazed through the entrance, dumbstruck at what laid beyond it.
"Behold, Lumen Histoire!"
Omake
"I'm so excited, mya!" Millianna said to Erza. "We're finally having a proper wedding, with you and everyone else attending!"
"I'm very happy for you and Natsu," responded Erza. "But, is two weeks long enough to plan a wedding?"
"Well, it isn't like there's going to be too many people," replied Millianna. "Natsu and I have talked about it from time to time over the seven years, and we agreed to keep the guest list small. Aside from Fairy Tail, only a dozen or so people were invited."
"Besides," continued Millianna. "While my Fireball was dealing with the aftermath of battling Tartaros, I've been planning out the ceremony for when you and the rest of the Tenrou Group returned! I've got this, mya!"
Erza smiled at her childhood friend, proud of how much she had grown up in the past seven years.
"Speaking of guests, a certain blue-haired outlaw might be there," teased the cat-like girl.
"Or maybe she hasn't grown too much," thought Erza, her cheeks matching her hair in color.
AN: To clarify, the two new members other than Team Sabertooth and Romeo are Yukino and Mest. Also, I do plan to write the match between Natsu and Gildarts.
That's all I have to say for now. Goodbye!