my guess is that the reminisced about a time when they were six, but by the time our blonde moved out, they were much older than that (guessing like 10 or 11 ~) and then the blonde comes back 6 years later making the characters +15. The author didn't really say he moved out when he was 6. They only remembered a time when they were 6...
this is my guess or author didn't really plan it through...or author wanted them to be 12 and that's just weird but in my head gonna imagine them 16/17.
Ok, so. They are definitly in high school. I found the only thing that gave age and I think its mistake. I think that one section where it says (6yrs) means 6 years prior and isn't the age they were at at that time. Like I think the japanese may have been 6年前 or something, instead of 6歳. That or like the person above said, it was a scebe from when they were six, not from when the events of six years prior happened. I wish I had the raws
That could definitly be it. Actually that makes a lot if sense. It makes so much sense I'm mad.
6th grader = 小学6年生 (literal translation being "elementary school 6th year student")
Shorthanded just to the the 6 and "year" (年) would literally translate to 6 years but mean they are 12 ish in age.
High context languages are a pain!!!
You have done it. You have found the answer!
I can't talk from experience (as the latest of late bloomers) but I'd think between 10 and 12 is probably normal to start exploring that stuff (you know, 'cause puberty). 6 definitly isn't. I think the major problem here would be if, during present time in the manga, they were 12, that is weird. And creepy for us, the audience.
I'm so confused by the second story. You're telling me they're TWELVE? Uhm I don't know if it's just me but... d-do six year old kids really masturbate