One morning at the penthouse, Spike, the girls, and Celestia were busy decorating the place for a party. Spike was helping Twilight and Sunset hang a banner saying 'Welcome Home Luna'.

“So, Twilight, run this by me again,” Spike started, “Luna is Celestia's younger sister?”

“That's right. Usually she's acted as Nurse at school, but in the last two months she's been on temporary leave.”

“Why is that?” Spike inquired, as Sunset answered.

“While Luna is a nurse, she's also a very skilled hacker, and has been traveling around gathering information on Grogar and where he is truly operating. After all operating from Micro Software's company building would be too obvious.”

“I see.”

“Thankfully her mission is over and is ready to resume her work at the school. While she can still operate here with her hacking.” Twilight said.

“What's she like?” the boy asked.

“She's very nice, though her social skills according to Celestia wasn't always perfect.” Sunset explained.

“She also liked to speak in a loud voice a lot to make sure everyone could hear her.” Twilight added, and the two girls giggled.

“But we're sure you'll like her.” Sunset promised.

“If you say so.”

Pinkie looked out the window and gasped, “Here she comes!” the group hid and waited for the right moment.

Suddenly entering the place was a beautiful woman a bit younger than Celestia. She had hair long and wavy dark blue hair hair with light and dark blue streaks. Her attire included dress shoes, dark blue pants, a purple shirt with a white collar that had a crescent moon symbol on it, and a white belt around the lower torso area. And her rack size was an H-cup.

Suddenly part poppers popped and noisemakers sounded, as the group shouted, “Surprise!”

Needless to say the woman looked around in surprise and was overjoyed. Celestia approached and hugged the younger woman, “Welcome back, Luna.”

Luna smiled and returned the hug, “Good to be back, Tia.”

“Luna!” the girls cheered, as they ran over and embraced her.

“Twilight! Sunset! Everyone! It's so good to see you girls again.”

“We really missed you.” Fluttershy said happily.

Celestia smiled seeing her students and sister so happy to see each other before looking over at Spike, “Come over here, Spike.”

Spike approached, as Luna saw the new boy. Celestia turned to her sister and explained things, “Spike, this is my sister Luna Equestrius. Luna, this is Spike Ddraig, the newest student at school and newest member of Team Starswirl.”

Luna got a good look at Spike and she checked him out making the boy blush, “So this is Shenron the Dragon Warrior in Eden?”

“Correct.” Twilight confirmed.

“It's very nice to meet you, Ms. Equestrius.” Spike greeted her respectively, with a shake of her hand.

“And I'm delighted to finally meet you, Mr. Ddraig.”

“Call me Spike.”

“We hope you don't mind, but Pinkie wanted to throw you a welcome home party.” Rainbow told Luna.

“No problem at all. I'd be insulted if she didn't throw one.” Luna replied, as Pinkie smiled knowing how much her parties mean.

“So come on, ya'll. Let's party!” Applejack declared, as everyone cheered.

So the party began with everyone having a good time with enjoying snacks, dancing, and catching up with Luna. Spike was taking this as a good opportunity to get to know the youngest sister.

Spike had been laughing at something humorous Luna shared with him, “Principal Celestia is afraid of chickens?”

Luna giggled, “Oh, yes. She tried chasing some at a farm during a class field trip when we were kids, and the chickens didn't take kindly to it and swarmed her.”

“That does sound bad and funny at the same time.” Spike continued to chuckle.

“So you find that funny, do you?” Celestia spoke up, as she stood behind Spike who gulped.

He turned around and stammered, “I mean in terms of bizarre stuff happening in childhood.”

“I see,” Celestia smirked, “Well, did you know Luna tried getting a tan on the beach and got so sunburned she had to go to the hospital?”

“Get out, seriously?” Spike turned to Luna who looked embarrassed.

“I spent the whole week shedding.”

“You two really are quite the siblings, huh?” Spike asked playfully.

“Well, uh...” the two stammered sheepishly.

“In any case it is good to have you home, Luna.” Celestia said.

“Thank you. And I just had to come home because after all Halloween is coming up. And you know it's my favorite holiday.”

“You a candy girl?” Spike asked.

“That and I love the thrill of scares and fright.” Luna said creepily.

“When we were teenagers, Luna was always regarded as the master of the night and fear.” Celestia explained.

“And I wasn't so easy to scare.” Luna put in.

“Amazing. So fearless.” Spike admired.

“So, Luna, have you found any leads on Grogar's whereabouts?” Celestia inquired.

“Sort of. I learned he doesn't always operate in the same place. He shifts around to other locations. Different buildings in different countries. There's never been a chance to predict where his next location would be.”

Celestia sighed, “Well, at least we know he doesn't stay in one place.”

“I'll continue to run checks on the previous places he's been reported at and see if I can determine a pattern.” Luna offered.

“See that you do, but for now let's just relax. It's a party after all.” Celestia reminded her.

Luna smiled, “Right.” and so they resumed their fun with the teenagers.

That night on the penthouse balcony stood Luna looking out into the city admiring the glow of the lights. Suddenly he felt something placed on her shoulders and saw it was a blanket. She turned and saw Spike standing there.

“Celestia told me you'd be cold.”

“Oh, Spike. Forgive me. I just happen to like looking out into the city at night.” Luna explained.

Spike nodded, “Celestia told me you always loved doing that. And I can't blame you. It is a beautiful sight.” he looked out into the city with her.

“It sure is.” Luna nodded.

“Luna, I know it may be an adjustment for you now that you realize it's not just your sister and the girls living here.”

“Oh, don't worry about a thing, Spike. I'm glad you moved in during my absence,” she replied, “It's always good to have a fresh new face around the penthouse.”

“Thank you.” he noticed Luna giving him bedroom eyes.

“Especially if it's a handsome young man.”

“Uh, thank you?” Spike answered with a blush.

Luna stood before Spike putting her hands on his cheeks, making Spike's blush increase. Suddenly found his face pulled deep into Luna's impressive bust.

“Luna?” he asked with his voice all muffled.

Luna smiled down at Spike, while resting her chin in his hair, “Spike, I look forward to seeing more on you on me and my sisters team.”

“Ahem!” someone spoke up grabbing their attention.

They looked over and saw Celestia standing off to the side giving them a stern look, “Well, good evening, sister.” Luna greeted without a care.

“Luna, that is no way to treat our boy resident.” Celestia told her sibling.

“But he's so adorably handsome, Tia. And I haven't had any contact with boys in months.”

“Luna.” she replied sternly.

Luna pouted, as she released Spike from her embrace allowing him to catch his breath, “Fine. I need to turn in anyway. It was lovely to meet you, Spike. See you tomorrow.” Luna walked back inside, making Celestia sighed.

“I am so sorry about that.”

“No problem. I'm just glad me and Luna are getting along so well for our first meeting.”

“So am I,” Celestia confirmed, “I'm actually glad she was able to make friends with you and the girls as well when they first came together.”

“Really?” Spike asked curiously.

“Yes. Growing up, despite how close we were. We did have an estranged relationship.” Celestia confessed.

“How so?”

“Because I was the oldest I was always regarded as the smartest, prettiest, and most reliable. And all the praise given to me by our family and friends while Luna was around always made her feel inferior to me. Because of that there was a time she completely shut me and everyone else out of her life thinking if we didn't need her then she didn't need us. I tried so many times to reach out for her, but she always ignored it. Until one day I wouldn't back down and she finally unleashed her deep emotions on how she felt about me and always feeling like she'd never amount to anything. I comforted her assuring her she didn't have to be like me and not let what others say about me affect her. It took awhile but she finally came around and opened up to me and everyone else. I had my sister back.”

Spike noticed Celestia smiling knowing how much her sister means to her, “Having siblings isn't always easy. Trust me, growing up with Smolder and Ember wasn't always a picnic. But in the end you're glad you have them in your life.”

“Exactly.” Celestia agreed.

“And I'm glad to see the two of you together again. Now it's like your family is once again truly complete.”

Celestia smiled, as she pulled the same stunt Luna did and held Spike's face deep into her bigger bust, “It's really complete because we have you as part of our family now, Spike.”

“Thank you.” Spike replied all muffled.

Celestia released him and spoke, “We should both turn in. Tomorrow is another day after all.”

“Ain't it the truth.” Spike replied, and the two laughed before heading inside. As they walked, Celestia held Spike close to her, which Spike didn't mind in the slightest.

Just a little intro for Luna before they spend Halloween in Eden, And Spike may have more bonding moments with the two sisters down the line