The Immortal Lord Searched for Me for Seven Hundred Years

Dual male leads, both powerful, fantasy xianxia, a great demon and an immortal, lovers who are both rivals, reunion after a long separation, sweet romance. I chose the wrong tag and selected historical romance. I don't know if that will affect anything. If you don't like xianxia, feel free to move along. A seemingly innocent but secretly cunning demon lord who loves to act cute and coquettish (the shou) VS a cold, proud, undefeated immortal lord who is devoted and quietly longs for him (the gong). Ren Xiao, young master of Yunjingze, got drunk at his birthday banquet and somehow transmigrated into the body of a great demon. By coincidence, the demon had the same name and appearance as him. The great demon wanted to cut out the heart of an immortal who had been dead for a hundred years. He failed to get the heart, but gained an immortal who was completely obedient to him. To get back to Yunjingze, Ren Xiao followed the immortal in search of a miracle doctor. But as they spent time together, he increasingly felt that something was off. Why did the immortal keep treating him and the great demon as the same person?