Riela, a sister who doesn't believe in God

Riela, a girl who lost everything in a war with the devil.

She is skeptical of the teachings about God and runs away from the convent under the excuse of a pilgrimage.

Riela is SFW and has no sexualized elements.

She doesn't believe in God, but she's intelligent and has a good understanding of theology because she studied for so long.

There's a secret element that's hidden, but I don't know what it is. Thrown in for you to make up your own mind.