I finished the anime and I still wonder what Kurisu said to Okabe in the first episode.
She pulls Okabe out of the conferance and says "Back there, you were going to tell me something, weren't you?" and Okabe responds "Back there?". Kurisu says "About fifteen minutes ago" and Okabe says "I don't have the slightest idea".
I guess it has (spoiler for the end of the anime)
something to do with time travel and world line travel in episode 23 and 24 but unfortunately I didn't watch those episodes that carefully.
However, what did Okabe intend to say to Kurisu, and where, and when?