Kaori is one the most caring personalities in the series. She is a classmate of Hajime's back in their original world. She admires Hajime for his "strong" personalty and is the only classmate who pays attention to Hajime's existence in class even if she is popular in their school. When summoned to another world, she receives the "Healer" job.

Spoiler

Kaori was unable to notice her love for Hajime until he fell in the abyss which inspired her to become stronger in order to search for him. After reuniting with Hajime, she then joins their dungeon expeditions after confessing to him.

Spoiler

In volume 6, while Hajime is off fighting the first of the God's Apostles alone. Kaori becomes gravely injured back at the capital while fighting off one of her classmates. After Hajime wins the fight he learns of Kaori's weakened state and decides to transfer the soul of Kaori into the body of the apostle. In doing so Kaori becomes stronger all across the board and over time she learns to use the same abilities the apostle used against Hajime.