I did check, and Yoshino's inverse form only exists as concept art. I looked up a lot about the character and never in the series does she inverse. This would mean there would be no role to base an inverse form on. And Rej is saying that Yoshino somehow has
2 forms when she only has her spirit form. Unlikely.
And did ekko say that Yoshino didn't exist or that the details that Rej was talking about didn't exist? Cause I bet it's the latter. No way would ekko miss something like that
especially if Yoshino is supposed to be one of her targets.
https://date-a-live.fandom.com/wiki/Yoshino_Himekawa#Inverse_Form__