In hindsight, the scene was actually supposed to portray the sheer ridiculousness of Chihaya’s strength and also her clumsiness. So that means Arato still has to be in that tree. 
It’s hard to translate that in the genderbent version, considering how it’s traditionally believed that men are stronger than women, but I have an idea: what if the reason why Kokoro insists on helping Arato is because she thought he was too clumsy to deal with it? She has all the reason to believe in her strength: surely she had done a rewrite on her strength before this, so she’d still be in disbelief that she couldn’t even lift the box an inch higher while Arato could carry it… with one arm, for the sake of exaggerating it further.
A funnier idea: what if the source of Arato getting pissed is the fact that his pants got ripped by a branch due to the fall? He was incidentally wearing cherry-patterned boxers, and didn’t want Kokoro to see, but she can’t help it. XD
I finally got around to do genderbent designs of the characters, drawn in the format of the anime poster! I’m very sure that there are other designs around the Internet as well, but here’s what I’m happy with. What do you think? 
I did say I was going to upload a compilation of sketches, but that’s for later~
