[4] Set in South Korea's fictional Silicon Valley called Sandbox, Start-Up tells the story of people in the world of startup companies.

Seo Dal-mi (Bae Suzy) is a bright and ambitious young woman who dreams of becoming Korea's Steve Jobs.

He finds out that Dal-mi mistakenly remembers him as a secret pen pal whom she thinks of as her first love, so he decides to work his way up in hopes of turning that misunderstanding into reality.

Choi Won-deok (Kim Hae-sook), Dal-mi and In-jae's grandmother, a corn dog shop owner, gave shelter to young Ji-pyeong (Nam Da-reum), an orphan and winner of a virtual investment competition.

Chung-myung successfully secured an investment for his startup but afterwards died from injuries sustained by a car crash on his way to the pitching.

Dal-mi is accepted into Injae Company as their COO, after she recited In-jae's words once also said by their father about him resigning to pursue new innovations that can eventually make old technologies and human work obsolete.

The friends all give different promises that could be borderline ludicrous if they win the bid, and Do-san says he will propose which surprises Dal-mi.

[14] Kim Jae-ha of Teen Vogue including it on the list of the "11 Best K-Dramas of 2020" said that "Start-Up reinforces the idea that no matter how fractured a family is, the ties remain – for better or worse" .