one time hand hold during first firework, that's just superstition
two time hand hold during first firework, that's coincidence
three time hand hold during first firework, now that's just fate
I like how route 1-3 doesn't involve his father at all which is understandable, they are classmates.
Route 4 and 5 instead heavily link his father in their story and further reinforced their background so you doesn't feel like their route is shallow.