Kaguya's mood soured when she heard what Rei asked her.
"You don't know?" She threw an incredulous look at him. "How did you know about me being sealed in the moon, then?"
"Well, there are legends but I would like to hear your version of the story." Rei shrugged. He didn't put much belief into all that crap told in the legends. Now that he felt the incredible potential of the being called Kaguya in front of him, he couldn't help but think these legends were all bullshit. Hagoromo and Hamura had no chance to win against her no matter if she didn't even start scratching the surface of her potential.
For a second, a wistful expression appeared on Kaguya's face as she reminisced about her past but it was gone as fast as it formed. With a cold expression, Kaguya distractedly reached for a cup of tea, not realizing how her hand shook. She took a long gulp from the cup and looked Rei straight into the eyes. Staring into his encouraging eyes, Kaguya gained a newfound determination.
It was a surreal feeling for Kaguya. She wanted to have someone to talk about these things for more than a thousand years now. Nobody, not even her sons, could provide any form of support for her but now... now that she looked at the strange man who appeared in her seal, Kaguya wanted... no, deeply desired to let it out.
Before she knew it, she started to pour her heart out to him.
Rei patiently listened to her story and had to admit, the legends were mostly correct. The difference was... these legends had a different way of looking at things. Kaguya had reasons for doing what she did. She wasn't some madwoman who was turning humans into wooden soldiers for kicks and giggles. As she explained what she did and why, her cheeks never dried of tears.
She started with how she was selected for the expedition to grow a chakra fruit. How she came to Rei's planet. How she didn't agree with the ways of her traveling companion and how she 'betrayed' him, knowing it would have been her undoing.
It was a story about a naive, young, and stupid girl.
She told Rei how she met her husband. How her heart fluttered when he talked about his ideals. How she, for the first time, fell in love, not realizing or paying attention to many important things. With hurt and tear-stricken expression, Kaguya portrayed how her happiness slowly changed into the realization that while she was the wife of her husband, he was a ruler and had a completely different way of looking at marriage than her.
She spoke of long lonely days and short nights of a passion that was slowly but surely burning out. Of how her maid was slowly becoming more of a husband to her than her actual husband. Kaguya simply put all of her grievances and poured all of her feelings from her apparently unsatisfying marriage a thousand years ago on poor Rei's shoulders, causing him to wryly ponder when he became an emotional support line as he silently listened to her.
Kaguya... eventually realized that she fell more for the fairytale ideals of her husband than him as an actual person. Her infatuation made her blind and that led her to a monumental decision. She confessed to Rei that she decided to take the chakra fruit and return back to the Otsutsuki clan. She was aware there would be a punishment waiting for her back home for what happened with her traveling companion but Kaguya also knew that if she brought the chakra fruit with her, it would be a negligible one. Instead, she would actually get rewarded right after she suffered a bit.
These plans were quickly destroyed, however, when one nice morning was ruined by a realization that she was pregnant. It was both a joyful and horrifying experience for Kaguya. While her maid was rejoicing like a small girl. Kaguya felt a myriad of emotions, most of them dark. She cursed her husband, she cursed her luck, she cursed herself for not being careful enough...
Rei found it funny. From how Kaguya described it, by the end of their marriage, she felt no satisfaction from having sex with her husband. She just bore with it because she thought it was her duty as his wife. Now she realized she was still stupid at that time and that she should have rejected him completely but... it was already too late to lament about it.
It was hilarious how she, a female Otsutsuki who should have had a hard time getting pregnant, actually got impregnated by a 'mortal' not when she passionately slept with her husband every night during the height of their 'love' but when the guy only graced her bed once or twice per two weeks for a quick release. Rei couldn't help but feel a bit of respect for her husband when he heard that. Thankfully, he could hide his amusement well. It wouldn't be nice to laugh into the face of a crying woman.
Kaguya knew she couldn't return to the Otsutsuki clan anymore. For that, she needed to kill her children first and that was simply not happening. She was happy to become a mother but it also chased her into the corner.
"It's ridiculous. There is always something that 'seals' my fate." She dejectedly said with such emotional depth, Rei sighed to himself and decided to reseat himself next to her, supportively embracing her small frame.
Kaguya then continued with her story, her words and tone a bit lighter as she leaned her body into Rei who felt a bit awkward.
Then, the entire debacle with her husband trying to kill her happened. Kaguya understood why he chose to sacrifice her to avoid the war. He was a ruler and had his priorities straight. He had to think about the well-being of his people. But... Kaguya had to think about the well-being of her children. She already forfeited her future and her life for them when she decided to keep them rather than return to her clan.
And so... she ate the chakra fruit.
Her life after that incident improved. She got stronger, became the ruler, and led humans to prosperity and peace. Deep down, however, Kaguya always felt anxious and insecure. Always awaiting the Otsutsuki clan to come and punish her... and her children. Eating the chakra fruit was the worst crime she could have done and she had no illusions the Otsutsuki clan would not realize what happened.
Her children were a big motivation for her. All she wanted was to raise them well, give them love, care for them, and make sure they would be happy. As such, Kaguya decided to make countermeasures against her clan.
Much to Rei's amusement, he bluntly told her he thought her plan sounded dumb and Kaguya blushed crimson red from embarrassment, unable to refute it.
Army of White Zetsu? What good would that do against the Otsutsuki clan? They couldn't be even considered cannon fodder!
"Instead of trying to create an army, you should have tried to master your own power and train your body." Rei gently chastised the downtrodden woman in his arms.
She sacrificed a massive amount of people in her quest to make an army... and for what? To create something as useless as White Zetsu? There was no wonder her legend portrayed her as pure evil.
'More like pure stupid...' Rei thought with a carefully hidden eye-roll.
Leaning his head down and looking at the fidgety woman in his arms, Rei realized one important thing.
In the end... she was simply a scared little girl who found herself shouldering the weight of an entire planet, knowing her clan would one day come for her.