Immortals and Demons Are in the Same World

The protagonist is Shi Yixin. He was accepted as a disciple by the dead soul of the demon god and joined the sect of the Immortal King. However, he was accidentally exposed and was regarded as the reincarnation of the demon king. He was hunted down, but was accepted by the True Immortal Yuanshi. In the end, the immortal and demon fellow practitioners became the Immortal Demon Emperor.