Demon Slayer: After raising Shinobu, I died in front of her.

(Rating just released, will increase later) [Single female lead Shinobu Kocho] [Not invincible] [Male lead is a Pillar + original breathing technique]
Ling Chuanche saved two sisters who were just very young children at the time.
He raised them as his daughters, giving them all the good things in life.
Later, they grew up and eventually became swordsmen.
However, on the very day Shinobu became a swordsman, she learned of his death.
In an instant, their world collapsed.
The male protagonist is an indigenous person, not a time traveler, and is 12 years younger than Shinobu Kocho. The book has a slow pace.