@greatninja3
Legal age in Japan.
Also laws aren't based on what's natural or the normal for attraction, just what we deem to be the age where a human is neurologically developed enough that we can trust them to make decisions about their own consent without being pressured or manipulated in some way by an adult. Sure exceptions exist where these sorts of relationships can be totally healthy. There are also plenty of cases where it's not, yet people will try to rationalize it as such. So we legally draw hard lines - if youre really serious you can wait a few years, and if you're willing to break the rules then you accept the risk.
Which is why pedophile accusations are often counterproductive. Suddenly it's an argument about what's natural human attraction and behavior, and not about ethical logistics. Ultimately what it comes down to is where as a culture you choose to draw the line - though then of course issues arise when cultures differ on this point.
I personally think the standard should be a bit higher than 16. But as far as fiction goes, I'm comfortable with it in this case. They seem good for each other, and I don't think Andou's pressuring or "grooming" her. And most importantly neither character seems to give a shit about the law anyway. A disregard for society and common decency is just sorta the tone of this manga; wthin the last to chapters a young girl was groped and someone choke-slammed a cop.