Ryan Cooper has three rules for Ethan Clark:

1. Don't call me big brother in public
2. Don't act together
3. Don't let anyone know you live at my house

Ethan Clark has always obediently followed these rules, acting like a stranger at school. At the opening ceremony, he suddenly collapsed from an allergic asthma attack, causing chaos at the scene. Unexpectedly, Ryan Cooper, who was giving a speech as the student representative, abruptly stopped speaking...

That night, the campus forum was buzzing with a hot post:

[Shocking!! The most handsome boy in our junior high and the most handsome boy in our senior high are actually "brothers"!]

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Ever since his father brought home a little mixed-race kid at the age of six, Ryan Cooper's life has been completely entangled with this clingy little guy whose Chinese wasn't even good.

Preschool Liam Clark: Brother Ryan, my classmate said he has a pretty "sister-in-law" today. What's a "sister-in-law"?

Ryan Cooper: His brother's wife.

Liam Clark: No! I don't want a "sister-in-law"!

Ryan Cooper: ...

Liam Clark: I'll be your "sister-in-law"! (Something's not right here...)

Ryan Cooper: Please study Chinese family relationships properly.

Liam Clark: No, no, I'll be my own "sister-in-law"!

Ryan Cooper: ...