you seem to care about titles a lot. the issue with age gap relationships, and specifically around late teens and early adulthood, is that the brain of a teenager is not fully developed. in this sense, how can someone with a fully developed brain (21-23) be romantically invested in someone biologically incomplete, who can't be fully conscious of their decisions?
however, titles such as high school student, when used to signify inexperience and youth cease to bear meaning at the age of 17. that's because the developmental progress of the brain is minor from 17 to 18, which is considered to be the legal age and the brain is also near completion. this is why even if the age gap between the protagonists were 3 years, it'd pose no problem.
if we were to talk in superficials, i'd argue that usually 20 yos and uni students become more childish as they enjoy a newfound sense of freedom, liberate themselves from the school way of studying, begin to discover hobbies that speak to their novel self and act on them. they become overwhelmed by the new world they're introduced to.
P.S. i suspect the ML works in a cafe or a mini restaurant. it is normal for restaurants to also sell alcohol, and serving or countering in such places is one of the best shots underage part time job hunters possess to gain experience. also.. adolescents working in bars is sadly common, although it's abnormal. oftentimes they work there out of need though, so it's not limited to this story for the sake of convenience, nor weird cus it's out of the blue.
i believe that this can depend on one's point of view. It is undeniable that people are free to be unaffected by their "age gap" as it is legal and doesn't reach anything concerning. Rather than the age itself, i often see people concentrate more on other aspects such as the difference in their experience, levels of education, legal status, and other factors. When it comes to something, people will still notice it and express their opinions about it, even if not much.
i dunno know, but even if it is technically okay, i still think people would feel questionable of a 21- or 23-year-old who came forward and said they were dating an 18-year-old who was still in high school. but again, this is just my opinion from what i’ve seen. the motive, though, is perhaps the most crucial factor (?) since it is very simple for an older person to take advantage of a person who is 18 years old or less and use that person's age as a justification. although that itself is just a general response and what is seen as the most worry in relationships that deal with age gaps even if it is Ok technically :3
The human brain isn’t fully developed until mid-to-late 20s. That’s why I said “stage of life”, because she is a university student and her brain also isn’t fully developed since she, ya know, literally turned 20 at the beginning of the story. The weird factor of age gaps tends to come in when there’s an imbalance of power, which there isn’t much of one here because both characters are still young and exploring life, just at two different stages.
I’ve also already been through college, and from my experience a lot of the overwhelming stuff really starts near the end of it when the realization that you’re an “adult” now actually sinks in. Everybody is different though, so it may tend to vary person to person.
Also, yes, in certain places of business, you do need to be a certain age to sell alcohol, that’s why I mentioned I thought it was weird. Irl places can lose their license to sell if they’re caught breaking laws regarding the sale of alcohol, but this is also fiction and a different country from where I live, so their laws might be a little different from mine *shrug*
So he’s able to sell alcohol, which I think you have to be 18 to sell in Japan. Which makes him at least a senior in high school, and she’s just freshly 20. So that means there’s not even really much of an age gap so much as a “time of life” gap. It is a little weird that he’s a high schooler working in a place that sells alcohol, but I’ve also seen stories where the student gets with their teachers, which could be anywhere over a 10-year age gap. Which is gross when you’re still a minor.
I’m not saying it’s otherwise normal for a newly legal adult to become attracted to someone who’s still in high school (I had friends who were still in high school when I was her age), but at least he’s OVER 18, as he said himself.
If he proves to be under that, yeah, I might drop it because he lied about his age, but other than that I feel like this might not be too bad of a story ¯_(ツ)_/¯