Mushoku Tensei: The Witch's Reverse Reincarnation

Rudeus is reincarnated in another world and begins a second life straight out of a wish-fulfillment novel.

But on the other side of Earth, the same rift in space and time forces a vast magical soul from the Six-Faced World into the womb of a Japanese woman.

Her father is a French nobleman and her mother a young genius doctor, yet she becomes a "stain" on the family because of her East Asian blood and her identity as a girl. The soul from another world devours the Earth's embryo, granting her terrifying intelligence. Her body is also forcibly matured by magic: at seven, she already looks like a girl in her early teens. She should be able to command the world with her intellect, but instead she is frail and sickly, as if the world itself rejects her.

Worse still, that heavy iron sword is merely her father's way of making her suffer "legally." On a magicless Earth, the magic inside her can only flow out, never in. Every time she is forced to swing the sword, her life force plummets and her black hair quickly turns white. Her peerless talent with the sword isn't a blessing, but a death sentence that drains her life.

She swears constantly and has a fiery, sharp tongue, convinced she's a monster with a terminal illness. Then, when she is seven, a thunderstorm strikes her and sends her back to the place where she was always meant to be.

In the other world, she looks at the green-haired boy before her, his face full of confusion.

"So you're the one who crossed through the rift and got me shoved onto Earth, where I almost died?"

Two souls whose paths were crossed by the same rift have finally met.

P.S. This work isn't under contract; I'm just writing for fun, so the prose and plot definitely won't be as good as those of great authors. There's more slice of life, and I'll try not to contradict the original setting, though I will add new details not in the original. The three primary colors are red. If you can't accept that, feel free to leave. Pure love, no harem, yuri.