The Lord of the Monsters by Huang He

9.20

As the Demon King Baize is on the verge of awakening, the immortal disciple Mu Qing sets out to the demon realm before the chaos spreads across the three realms, seeking the magical instrument Qingluan Mirror to slay the Demon King. By a twist of fate, Mu Qing embarks on the journey with the little demon Chaoyan. During their adventure, they grow to know and love each other. Just as they are about to fulfill their mission, Mu Qing discovers that Chaoyan is the reincarnation of the Demon King, marking their relationship with a destiny of tragedy despite their deep bond across two lives.