They're not adults, they died while still wearing school uniform, they were students
The author is korean so i think they forgot to convert korean age to international age despite obviously drawing a western kingdom story
In korean culture, they consider newborn babies as 1 year old already (they consider 9 months in the womb as 1 year)
So when arien said she's 25 in chapter 1, it means they died when they were 19 in korean age (means their actual age is 18, 18 is the last age of korean being high school student), then they lives 5 years as rurahel's child means they're 6 years old in korean age, so 19+6 = 25
Besides they're not in their mid-twenties, actual 25 years old already gone through grown up environment by graduating from college, going to job, and experiencing adult life,
People become adult NOT because of age but because of experience!
These twins died as high school students and living their 2nd life as kids, so they're not adult yet
I agree with everyone here. These kids are so skeptical of everything but yet they easily trust ppl they shouldn't. wtf. they are in their mid 20's. come on! can we at least have some consistency. also communication, Jesus. I'm getting fed up with this story. probably will drop it after I see the red wolf.