"It's been two years since [the Black Widow and Captain America] appeared, and now both are agents of S.H.I.E.L.D. fighting in the streets," Johansson said per SuperHero Hype, via Refinery29.com. "We are not superheroes flying side by side. They help each other because we are fighting in a similar way. It’s a working relationship."
Johansson also discussed her relationship with actor Chris Evans' Steve Rogers and that unforgettable escalator kiss which went viral when the photo was taken in Downtown Cleveland's Tower City Center.
"By a series of unfortunate encounters, they will be in a situation in which their friendship becomes more intimate. They share many similarities because they live on the defensive without relying on anyone. Also, the two have been working for the government throughout their professional careers. With their friendship they begin to question what they want and what is their true identity."
Captain America: The Winter Soldier releases in theater on April 4, 2014.
[Related story: CAPTAIN AMERICA: THE WINTER SOLDIER's Black Widow and Steve Rogers 'Relationship' Teased by Scarlet Johansson]