In Nagamori's route. I was pretty disappointed by the route as a whole, considering how much of a Jerk Ass Kouhei was, but even still Mizuka's doggedly loyalty to Kouhei is heartwarming in and of itself. The moment in particular that got me is when Kouhei is convinced everybody has finally forgotten about him, even Mizuka, though she'd remembered him longer than most. He's walking down the street, depressed, and sees Mizuka on the other side of the street. Since neither acknowledges the other, he carries on, resigned to being forgotten. As he goes to cross the street, she crosses at the same crossing. Even as they meet, they don't say anything...instead, Mizuka grabs Kouhei and hugs him from behind as he passes her, right in the middle of the street.
Mio's entire route as a whole. She's mute, so she has to learn to express herself by face and body language. So if you're playing her route and Kouhei and her become romantically involved, she chooses to express affection by hugging. A lot. How many boyfriends in the world get as many hugs as Kouhei does on Mio's route? And the epilogue even concludes with Mio hugging Kouhei's back...and continuing the hug for the entire length of time that Kouhei goes into a long internal monologue about how troublesome Mio is that she keeps getting lost. Just because Kouhei's "back is warm." And when it isn't a hug, Mio tends to hang on Kouhei's sleeve. It's like she thinks Kouhei enriches her life to such an extent that Kouhei's entire physical presence is a source of goodness to her. It's not really a dramatic moment of heartwarming, but this kind of innocence doesn't show up often in fictional depictions of romance, which focus overmuch on kissing for example. Plus, since it's later revealed that Mio is also a childhood friend(and that Kouhei gave her something precious as a child), you get the warm fuzzy feelings of a long awaited reunion ...without the Jerkass behavior the above Troper mentioned that Kouhei displays on Mizuka's route.