Bucky had a fear of the doctors office, even S.H.I.E.L.Ds. You couldn't blame not after everything he ha been through with HYDRA. Steve couldn't make go with Bucky this time has he was on a mission in Europe that is estimated to take a week, before it is completed. Sam was with him, so he was out of the running, and Nat was visiting Clint. which left you as the only person he was comfortable around.
You weren't as close to him as the others, but you still had a small bond that made him feel calm when he asked you to join him. You of course agreed, understanding his fear. During the appointment you asked him about the 40s to keep his mind at bay, but also making sure not to over step the doctor if the needed him to do something, or ask him a question.
It was going well, until the doctor asked; "I know Captain Rogers doesn't agree with this test, but where he isn't here this time, do you min if we take a blood sample? To see if there are any differentances between yours and his Super Soldier Serum."
Bucky stayed silent for a minute. Taking his time to answer. "Sure"
You could see the regret on his face as soon as he saw the needle. His medal arm clenched, worry filled his eyes. In a desperate attempt to distract him, you did something you knew probably was the greatest idea. You kissed him.
