Xiao Mowang De Lian'ai Gongke

Yan Jin is the young prince of the underworld, known as the Little Demon because he was so unruly. The Little Demon was influenced by all the TV he watched into thinking of himself as brave, heroic, smart, cute, and invincible. He thought he would have a harem of girls at his command. But then our four-year old Demon Lord met that three-year old girl, and he found himself putty in the palm of her hand. The domineering but innocent young Demon Lord is about to learn a lesson about love!

(Source: Bilibili, translated)