So Anakin and Padmé adopted Ahsoka. Not long afterwards everything changed and Ahsoka ended up on her own not knowing that she had a little sister and brother.
Almost 16 years have passed. Ahsoka has been secretly working for Senator Bail Organa as  Fulcrum for a while. During this time she meets and becomes closed to Leia. They share a strong bond that nether can explain.
As Ahsoka looks into what happened to her master she starts to find out about Padmé's death as well. However, learning the truth can be hard when telling it means losing something you didn't know you had.