Have you read any novels about the Demon Emperor?

It was about a soul transmigrator (I forgot her name) who fell in love with the Demon Emperor. The first time they met was when the Demon Emperor occasionally came to the lower realm. Then, the Demon Emperor helped the female protagonist control the divine fire. The third time they met was when the female protagonist was attacked by pretending to be a "family member." The Demon Emperor saved her. Then, the two of them came to a forest to train the female protagonist. Later, he came to a certain academy to study. When the female protagonist was in seclusion, the Demon Emperor returned to the Demon Realm. When he came out of seclusion, the Demon Emperor's secret guards followed him to a certain forest. Later, he came to the Immortal World and then to the Demon World. The Goddess of the Divine Realm was afraid that the Female Lead would snatch her position, so she assassinated the Female Lead. There seemed to be 9 or 10 types of divine fire, and later on, the female lead had them all. There was a princess in the Demon Realm who said that she wanted to be a concubine when the Demon Emperor married the female protagonist. Her dantian was destroyed by the female protagonist. The Demon Emperor and the female protagonist both had the same ring.