Worstgen
TheAncientCenturion
I def think he had the idea that Kakashi killed a teammate, but IMO I don't think he fully established a Rin character.
Shiroyru
Obito was name dropped as early as the Chunin Exams. I think he at least had planned out Kakashi Gaiden, Obito being saved by Madara, and Kakashi killing Rin in front of Obito. The finer details might not have been worked out til later
soupongo
Am I remembering right that Obito was name dropped the same chapter we first see the Akatsuki?