Well, this might sounds insane but regardless of what happened in this episode, I made my own deduction of this series. Hopefully it’s untrue but if it turns out to be the actual plot of this series, I’ll be like overhyped of my deduction skills.
I can sense another time travel cycle here. Here’s how:
Since Hina received the hairclip from Aoba, she might wear it just like the Hina that Aoba knew. At a certain time Aoba might get killed for some reason & then as soon as Hina learns it, she travels back 74 yrs earlier to fetch another Aoba there. After that, she sends him all the way back to the future again. You can tell there’s another cycle going on here.