Why did Uchiha Kei believe that Kikyo was Karin's mother?
Because looking back, everything about Uzumaki Kikyo's situation when she was rescued perfectly matched the labels attributed to Karin's mother in the original manga—who, notably, never even appeared in a full panel.
She was from the Uzumaki clan, imprisoned and used for human experimentation in the Land of Grass, deprived of her freedom—her age also lined up. And despite being an Uzumaki, she had never once appeared in canon. Everything pointed to Uzumaki Kikyo being the mother of one of the manga's beloved side characters, Uzumaki Karin.
Of course, there was always the chance the Land of Grass found another Uzumaki to exploit and Kikyo died quietly, forgotten by history.
After all, in the real shinobi world, anything was possible.
Regardless, there was no way Uchiha Kei would ever let Kikyo return to the Land of Grass to fulfill some twisted 'destiny' of giving birth to Uzumaki Karin. From the moment she came to the Hidden Leaf, she was already their protected little sister.
Once inside the house, Uchiha Kei headed straight for the kitchen and greeted Minato Namikaze, who was busy cooking. The two moved in sync to prepare dinner.
Before transmigrating, Uchiha Kei had lived the long and lonely life of a corporate drone—and like many single men, had picked up various cooking skills to get by. After arriving in the shinobi world, those skills proved quite handy.
As an orphan from a branch family who had moved out of the clan compound early, Kei had long since revived his culinary talents.
Minato, as Kei's closest friend, had already tasted the unique dishes Kei brought from his past life's homeland.
The distinctly foreign cuisine quickly became one of Minato's favorites. As another orphan, Minato was incredibly proactive and eagerly learned the recipes from Kei.
Kei was more than willing to share, and he was just as curious about learning traditional shinobi world recipes from Minato.
Over time, the two began cooking together frequently, naturally assisting one another in the kitchen.
These joint cooking sessions became a regular occurrence. Even though their culinary lessons had long since ended, teaming up in the kitchen had become a habit.
Now, whenever either of them hosted a small get-together, it was second nature to head straight for the kitchen and start cooking together.
Under the skillful hands of two men perfectly suited to be doting dads, a full table of colorful, fragrant, and delicious dishes soon filled the room. Four voices rang out in unison: "Let's eat!"—a warm domestic atmosphere surrounding them.
The sense of harmony during the meal made it feel as if the four of them were a real family.
And in truth, that wasn't far from reality. All four were orphans. Uchiha Kei and Minato had known each other since childhood and grown up as close friends. Later, Uzumaki Kushina arrived in the village and, influenced by Minato, joined their little group.
Then Uzumaki Kikyo was rescued—and became part of their circle too.
They had truly grown up supporting one another. Not blood relatives, but family all the same.
These small meals helped keep that bond alive.
During dinner, they chatted about recent events.
Minato shared amusing stories from his missions—nothing confidential, of course.
Kushina talked about gossip she'd heard from the neighbors, which was her favorite pastime.
After all, as the Nine-Tails' jinchūriki, Uzumaki Kushina lived under heavy surveillance and wasn't free to leave the village. Her daily life was more restricted than even her son Naruto's would be.
Still, she had no complaints—especially with a boyfriend like Minato and a mentor like one of the Legendary Sannin, Jiraiya.
Then it was Kikyo's turn. She happily shared her experiences training with the village's sealing corps.
As a member of the Uzumaki clan, born with exceptional sealing talent, she was a perfect match for that department.
Even though she hadn't received any formal education for the first twelve years of her life—and had been illiterate when rescued—she'd received top-notch education after arriving in the Hidden Leaf. And with Kushina's guidance as her clan elder, her progress was rapid.
In just four years, she had been promoted to genin via special recruitment. Now, she was about to be fast-tracked to chūnin. She shared the news with genuine excitement.
Normally, you'd need to pass the Chūnin Exams for such a promotion, but as a special recruit, Kikyo was allowed to skip that.
Everyone sincerely congratulated her.
Even so, Kikyo anxiously kept glancing at Uchiha Kei, afraid that he'd feel hurt.
After all, Kei had worked hard for years and was still just a chūnin, while she was being promoted with relative ease.
Only when she saw that Kei was truly happy for her—no trace of resentment—did she finally breathe a sigh of relief. The joy on her face was impossible to hide.
Minato and Kushina exchanged a glance and smiled.
If this bond turned into something more, they might actually become in-laws.
And honestly, that wouldn't be a bad thing.
Finally, it was Kei's turn to share. He spoke about the genjutsu-based game project—not to Minato, who had already experienced it firsthand, but to the two girls.
Minato, excited, chimed in with his own firsthand impressions. The two men described the genjutsu game's immersive wonder so vividly that the Uzumaki girls were instantly intrigued, eager to try it for themselves.
Despite the game's activation requirements being rather complicated—and suspiciously obscure—they trusted Kei completely. Just as Minato did.
But Kei turned them down.
That night, he still needed to preserve his chakra and mental energy to refine and repackage the game.
Even though his chakra and eye power had recovered, he couldn't afford to let the girls try it right now.
Of course, Kei was honest and explained the reason. He wasn't about to do anything that could be misunderstood.
The Uzumaki girls and Minato were disappointed. The sisters because they couldn't try the game, and Minato simply because he wanted to keep playing and reach the ending.
Still, no one blamed Kei. They just looked forward to the next opportunity.
Then, Kei asked Kushina a question that had been on his mind all day.
"Kushina, you're an expert in fūinjutsu. Do you think it's possible to repackage the game into a seal and embed it into a scroll? That way, a player could just unseal it and instantly play."