My Rival Became a Brat and Turned Into the Biggest Green Tea Under My Wing

Rumor has it that after Shen Qingjia shrank, the Demon Lord Zhong Jiu went to tease him three times every day.

The first time, Zhong Jiu lifted him by the collar. "Shen Qingjia, call me Grandpa and I'll give you candy." Young Shen Qingjia, eyes red-rimmed: "...Big Brother." Zhong Jiu, blushing despite himself: "Ahem. I'll let that pass."

The second time, Zhong Jiu sat the little one down on the demon throne. "From now on, you're the lowest-ranking servant in the Demon Palace!" Young Shen Qingjia tugged on his sleeve and muttered softly, "...My feet are cold. Hold me." Zhong Jiu, stripping off his robe in a huff: "What a nuisance! Come here! I'll warm them up!"

Later, Shen Qingjia returns to his true form, holding a long sword to Zhong Jiu's throat. His voice is cold as snow. "Still calling me a servant?" Zhong Jiu looks at the face he's dreamed about day and night and gives a cold laugh, ready to fight to the death. But then the aloof immortal suddenly lowers his eyes and hooks a finger around his, just like he did as a child. "If you don't call me that, I'll warm your feet again tonight."

Zhong Jiu: ...Damn, he's acting on me again! But I love it!

Thesis: After picking up your mortal enemy as a child, you have no choice but to raise him.