@phil777 Ehh, different background different culture, couldn't tell.. Legality is subjective for each culture and society. Maybe it's illegal in the western countries (idk cmiiw, still learning their values each day) but
some eastern countries have "age difference standard" where so long as the age difference is not exceeding certain point, it still counts as "legal" (but this policy starts to be phased out due to underage marriage issue, etc) while a 40/60 yo marries someone half their age will be frown upon although it's legal.
Also the series has a way to circumvent this problem so it won't be so problematic that I won't tell because it's a spoiler (but maybe you already know about this) but that's still far away ahead (and hopefully this manga won't be axed, if so the LN is the only thing that so close to that plot point after the WN of course).