I had a thought, this part, I wonder whether Mizuhara actually being sick would be better, like many other Romcom would do it, but I decide this awkward situation is better, it shows how there are times where there's nothing you can do directly, but in the back of your mind you still want to help regardless.
Most really would just go off when told to stay away repeatedly like that, but this guy, he's stubborn, no matter how uncomfortable the situation make him feels he wants to help.
And in the end it paid off, she did feel better when she knows there's someone else there that cares about her 24/7 still.
I'm not sure her story about the choco being from when she was 14 means her first menses also came that late for her? Tho probably just a random craving when feeling moody.