Sounds like what the IC is doing is sort of like backstory? Perhaps you could bring it out somehow after they meet.
For example, a kids’ story: MC and IC are both at summer camp. IC is in a different cabin but gets moved partway through the story because there was an issue (maybe IC got in a fight) in the other cabin.
So the MC/IC throughline doesn’t really begin until they meet (obviously) but the IC could tell the story of what led up to the fight, and the MC might react to what happened after the fact. This could even be part of their conflict, the way the two react differently to the same event which led to the IC being in the picture.
Does this make sense?