What Tyrant? He's the White Moonlight I've Always Longed For

[Both leads are devoted to each other + redemption across worlds + unhinged + sweet + 1v1 with intense mutual attraction + they raise each other]

Cheerful, chuuni, laid-back bottom (Si Zi) VS gloomy, violent top with little regard for morality (Lin Ruku)

Si Zi was born with a heart condition and abandoned at birth. Before he was even a year old, he was sent to a secluded villa to be watched over by a nanny, and was forbidden from going out on his own.

By chance, he opened a door to another world.

This dessert is delicious. I'll bring it back.

That toy is fun. I'll bring it back.

This kid... is so cute. I might as well raise him too.

He never expected things to get completely out of hand after that.

The villa's servants were horrified to discover that the young master seemed to have developed a delusion. He often smiled at empty corners, calling out “Big Brother” in a clear, sweet voice, and the servants had repeatedly heard him muttering to himself.

At the same time, strange things started happening in the villa. The maids fled one after another, and even the steward in charge of keeping watch was so terrified that he ran away.

A certain trespasser from another world merely smirked at all this. The next second, he bared his teeth at the person who had started it all. “I couldn't stand watching them bully you.”

Si Zi was helpless.

Si Zi sighed.

Si Zi had no choice.

He'd taken this big brother for himself, so even if he had to cry, he'd spoil him.