Fashion designer student Mo Ran that lacks the money to pay for models to use his designs so whenever his homework assignments need models wearing the outfits he just asks his husband to model it for him.
Chu Wanning wants to say no at first but since it's for Mo Ran's grades and
since his face won't be showing (Mo Ran would have to kill his classmates for daring to look at his man if that happened), he agrees.
Turns out he's pretty good at this modeling thing, and since Mo Ran had been designing everything with his measurements -- truly a coincidence,
his husband says, and Chu Wanning doesn't truly believe him --, all the designs fit him perfectly enough that he simply adds them to his wardrobe overtime.
When Mo Ran graduates and his slow-fashion brand grows, Chu Wanning remains being the main model for his fancier pieces.