Set in contemporary Seoul, the story follows college student Hemi, who unexpectedly falls in love with a coffee vending machine named Jin. Jin is not merely a machine, he is a samurai from the Sengoku period who, after being betrayed by assassins, wished to be reborn with an invincible steel body. To achieve this, he transformed into the vending‑machine form, preserving his warrior spirit while dispensing coffee to the city.