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Her hands nervously rubbed against eachother, gaze fixated on the steel appartment door in front of her. She slowly reached her hand towards the doorbell, contemplating if she should press it right now or wait a few minutes until she had finally calmed down enough to not embarrass herself in front of the two people she was about to be greeted by. Ultimately, that choice was taken from her as the door swung open and the cheerful gray haired man let out a loud and excited "HEYYY!". A quiet pat of feet could be heard coming from behind Byakuya, and soon enough a mop of green hair popped out from behind the man. Round and curious red eyes looked you up and down, then over to Byakuya.
"Byakuya, why are you yelling this loud? It's so unnecessary, plus, she looks so scared... I honestly feel sorry for her right now." The kid's voice was rather monotone, his eyes fixed on the woman in front of the two of them.
"Don't be like that, Senku! Say hi and introduce yourself to her instead of judging me..." Byakuya answered quickly, throwing an appologetic look towards the woman standing in the doorway.
"Yea, yea, old man." The boy said. She was surprised to hear him call Byakuya an 'old man', but ultimately let it go as the man was obviously used to it. "I'm Senku, and I'm a scientist." He said, rather bored. Only after his statement did she notice the white lab coat looking shirt the boy was wearing, two pens in the pocket by his chest. He looked like a little professional. She was impressed by his confidence, and she noticed that he was obviously very smart and very mature already. Chuckling a little, she remembered herself when she was younger and found that there was a certain similarity between her child-self and Senku, both having an obvious interest in science.
"My name is y/n, I'm your dad's girlfriend. It's very nice to meet you! May I ask how old you are, little guy?" She tried to sound confident, but it didn't come out that way as her voice wavered slightly in the beginning. She crouched down to be on eye level with the kid and tried to analyse his expression. For a split second she could see the slightest hint of irritation on the boy's face, but he went right back to its previous unbothered look before answering.
"I'm nine, and I'm not a 'little guy'..." He said as he looked over to the side, almost as if he was rolling his eyes at her.
"Don't be rude, Senku. She was trying to be nice, not insult you." Byakuya quickly said, a stern look on his face as he gazed down at his son.
"Yea, yea. I'll be in my room, I need to finish the experiment I was working on, Dr. X sent me some new information so I can't let him wait for my answer." The kid said, tuning around mit sentence and starting to walk towards the back of the appartment, pinky picking at his ear.
As soon as he was out of sight, Byakuya's eyes met hers. He had a smile on his face, knowing exactly what was going through her head at the moment. His hands moved to hug her for the first time, before sliding lower and pulling her closer into him by her waist. Foreheads pressed together, he looked at her lovingly and moved to peck her nose, then her cheeks and finally her mouth.
"He reminds you of yourself, right?" He asked with a grin on his face. She nodded and hugged him tightly. "When you said he liked science I ceratinly didn't expect him to be this far into it already..." She whispered into the juncture between Byakuya's neck and shoulder, hands moving up and down his back.
"Let's get inside, hm?" He asked, moving one hand from her waist to the door as he pulled her inside with him. She slid off her shoes and jacket, placing the shoes next to a few other pair that were strewn across the ground and hanging her jacket on one of the hangers Byakuya handed her.
The day passed by quickly, with Byakuya showing her around the apartment and explaining that she might be shocked when she gets to see Senku's room. He moved his hand to the door and knocked three times. "You can enter", the voice of the boy could be heard through the door. As Byakuya pushed down the doorhandle and slid the door open, her eyes started to wander around the child's room. Not even a second later she saw all of the equipment on the shelves, pieces of some kind of project on the ground in a corner. She was fascinated by all of the stuff the boy owned, but what fascinated her most was what Senku was currently doing. She and Byakuya moved closer, gazing over his shoulder. He was sitting in front of a laptop typing out a message to someone, but it wasn't just anybody, it was Dr.X, the nasa scientist she knew all too well.
Deciding to not disturbe him, she thought that not saying anything was the best option. She moved to look at Byakuya, signaling for him to go outside again.
---
Later along the day, almost night already, her and Byakuya were preparing dinner together. The vegetables and meat in the pan was sizzling, and the noodles in the pot were boiling just fine. The man was standing right behind her, arms around her waist and head placed on her shoulder lovingly.
"It's almost finished, would you mind calling Senku for dinner?" She asked him, turning around to give him a peck on his cheek. He nodded and moved towards his son's room.
Not much later he returned, informing you that he will be with you in just a second, after finishing his chat with his 'mentor', as Byakuya called him. She nodded and turned to finish the final steps of preparing the food.
As she was putting the vegetables and meat on the plate, she heard the patter of Senku's bare feet moving towards the kitchen. They came to an abbrupt halt when he spotted her. But wasn't the woman he was shocked to see, it was rather what she was wearing. From the front, her clothes might have looked completely normal to any person, but when he spotted the logo on the back of her white shirt, his eyes lit up with joy.
"Ahhh, Senku! You finally finished your chat, let's-" Byakuya stopped talking when he noticed his son's gaze fixed on his girlfriend's back. Moving his eyes to the same direction, he found the reason for his son's sudden surge of happiness: the big NASA logo right in the middle of the shirt's backside. He rubbed the back of his neck, remembering that he had never actually told his son where he met his girlfriend.
"Dad! Why didn't you tell me!", he said as he quickly walked over to the woman preparing their food. Before Byakuya could say anything, the boy's hand had already moved to tug at the hem of her shirt. She turned to look down at the boy standing by her side, letting out a 'hmm?', as if to ask him what he desired. "Do you know NASA?" He asked, his eyes shimmering with excitement. "Yes, Senku, I actually work there, you know? Your dad didn't tell you?" She responded while looking over at Byakuya with a confused expression. The man just stood there frozen, still rubbing the back of his neck with his hand as he shrugged.
"Do you help building the rockets too?" He asked, smile even brighter than before. When she nodded in approval, he let out a loud 'WOOOW, you're so cool!'. She chuckled as she patted his head. "If you happen to have any questions that you need to be answered immediately, you can always ask me and I'll try to give you the best answer I can, ok?" She asked, and the boy happily nodded.
And that's how Senku found a second mentor, which was also his dad's girlfriend.