When Naota, granted all the powers of Atomsk and wielding a double bass guitar as a weapon, faces off against, overpowers, and disarms Haruko. As his finishing move, he divebombs at her with full speed... to tell her that he loves her and to sweetly kiss her. Her genuinely surprised expression helps.
Another one happened earlier in the episode when Haruko and Canti suddenly return after (just as suddenly) disappearing for a while. At first, Naota acts just as irritable as always, but once he finally gets her alone, hugs her and starts crying, showing for the first time that he really does care about Haruko.
And also at the end of the manga, when Haruko's 'superior' appears out of Naota's head, claims that Haruko is on the lam...and then kisses Naota, revealing that yes, Haruko is on the lam...and she's right there. Notably, Naota isn't fooled for a second, and says he wants to kiss her.
After Kitsurubami attacks Canti with a sniper rifle and ends up in the river, Canti shows up, and she unloads on him with both pistols from point blank. After a cutaway, there's a shot of her clutching her gun and looking surprised. Cut to the wide angle, and it's Canti offering her a hand. Aww. The next time we see them, she's standing and her eyes have turned to hearts.
The ending. Particularly, Haruko asking Naota if he'd like to join her. Her retracting the offer also counts, as both instances prove that she really does care for Naota. Compare this to her ambiguous expression when Naota hugged her earlier.
The revelation that Ninamori and her parents appear to be working through their issues and may end up reconciling.