I like how Komura stutters a bit when he says they're going out. Its a nice detail that shows he's still embarassed to say it, but that he chose to say it anyway.
also Mie letting it slip not once not twice but thrice (4 times if you count the hug) is absolutely adorable
also I imagine one day when Komura wants to propose he's gonna have a perfect plan and time and place and everything. then Mie san is gonna smile at him or say she loves him and he'll gets instant K.Oed and falls to the ground. and then he thinks about how much he loves her and just proposes on the spot