This one was short and sweet. The storyline had a huge potential, with the actors having a seemingly great chemistry, but was unfortunately not harvested. It seemed to stretch a bit too long and there were unnecessary scenes which added little to nothing to the storyline. This led to there being less time left for an ending, making it seem forced and unnatural. Instead, adding more scenes for storyline development or even just the acceleration of this very plot would've proved to be excellent.
It had some beautiful meanings and concepts or stereotypes handled. Such as the "sex-taboo" in Japan or other Asian countries. Or the lack of awareness about the LGBTQ+ community itself like Nagisa pointed out. "After reaching puberty, a kid starts to feel attraction towards the opposite sex." Etc.
The chemistry was so amazing at certain points that it left you with a feeling of wanting more. Which was left unfulfilled, but still a sweet aftertaste. Maybe adding a bit more of character background even to Shun's role would serve the purpose! Almost felt like Shun was nonchalant throughout except for the part where they searched for the keys together.
The funniest part though, for me, was the mom's technique for getting over breakups. HILARIOUS X"D