Getting the band of burned-out adults back together, it would seem.
Ayase holding a different place in Chihaya's heart than Mio makes perfect sense. Mio is someone Chihaya...probably thinks she hates, but I'm gonna guess it's a level of rivalry that feels like hatred but in that sort of "love & hate are the two ends of a horsehoe" sorta way. They're inseparable, but up to now all their interactions and perceptions of one another are cast in a negative light, because of who each represents to their counterpart.
Ayase, though, is Chihaya's rock--a steadfast presence in her life since early childhood. She's also the one who did reach out to Chihaya, and pulled her out of her stasis. Sure, Ayase used Mio to do it, but she's still the one who wouldn't let her friend remain trapped inside, shut down and pining for something thought forever lost.
Ayase might feel like Chihaya never looked her way, and in some cases that's probably true--after all, the only thing ever on Chihaya's mind was running...except when it was the pure freedom that comes from constantly moving, as can be seen in dragging her friend off to play hookey in that flashback. But that sort of "dismissiveness" is only born of Chihaya's fixation, and not of her estimation of Ayase as a person or as a friend. If it were, she'd never have followed Ayase out of her house and on this road to redemption.
I'm willing to bet that the moment Chihaya gets to a place where she can actually reflect on it, she could confirm that Ayase holds a very special place in her heart, and in a very real sense she deserves the credit for Chihaya getting to this point, even. And I look forward to that moment, and Ayase getting to hear it affirmed.
Thanks for the TL.