Kate and Yelena finally started dating. Kara and Lena are dealing with the aftermath of Leslie's reveal. More and more stuff happen, with drama and trauma being added into the mix.
Kara and Lena have been friends for a few months. Lena and Kara wanted to pursue a relationship, but after Lena found out about Kara being Supergirl she was too scared. She told Kara they should just be friends. Until now.
(Kara and Lena's relationship as it begins and progresses. Also, Kara needs some work on controlling her powers with Lena.)