A new member - Sofia - joins the Avengers. Nobody really knows who she is, but there is one person who knows her very well, someone who was the most important person in her life long, long time ago. How will she feel around the Avengers? Will she be good enough for the team? Will they get along? How will she cope with her past? [some parts of the story are inspired by Black Widow movie a lot #spoilers] [no smut here, just fluff] [Sofia and Alina are the only characters I own, the rest is owned by Marvel]