basically in korea, people are 1 years old as soon as they are given birth to. but in all other countries like when you were born you are still 0 years old.
so in korea when you're born you're 1 years old. and every year on january 1, you add a whole year to your age AND on your birthday another year is added. so basically you add between 1-2 years on top of your age in korea if this makes sense.
so for example: say a baby is born on december 31, 2020. and the one day later, it's january 1, 2021. technically, the baby is just one day old, but in korea he would be a 2 year old baby.
that's why if you're 32 in korea, your actual age is 31 or 30 anywhere else depending on your birthday.
that's also why you become an adult at the age of 20 in korea, which means you're basically 19-18 and considered an adult now.
it's not about the translation, the story goes by the korean age, so when the author specifies their age, it's by korean age, which means they're still minors.
even in one of the chapters where cirrus and skylar stay overnight at the sauna, cirrus says it himself that they are minors and it's a good thing the sauna even let them in when they're underage.
Don't worry guys, the next ep is going to be torture but followed by it is bliss( no sex scene shown that's the bad part)ლ(´ڡ`ლ)