There not that bright...
It never says he disappeared for years. He disappeared since the 2nd day of high school and when he came back he's been missing for months without studying and he's studying hard so that he can catch up with Zhan and enter a good university together after they graduate high school.
Chapter 48, page 1
“I forgot already. It’s been too long.”
He’s already graduated by the time Jian Yi returns.
Chapter 224, page 12
“Everyone’s in college, I’m still repeating.”
Page 11 I mean (224)
This is gonna be long af but I’ve reread this and analyzed it a lot. It’s impossible for them to be in HS.
http://www.mangago.zone/read-manga/19_days/bt/311115/Ch45/1/
http://www.mangago.zone/read-manga/19_days/bt/311116/Ch46/1/
This is when they are adults. Zhan lives alone while right now he lives with his family. He says Jian Yi disappeared WHEN he was in HS meaning he is no longer in HS. He disappears on the second day. So this is why they cannot be in HS right now because Jian Yi doesn’t even attend HS with them.
Some people think it’s happened already but those other kidnappings weren’t years long only a couple of days. Zhan also becomes cold after it happens and right now he’s still nice to Jian Yi. It’s also shown that Jian Yi as an adult is still finishing HS while the others either already finished it and are in University or are working. Adult He Tian has a car-right now no mention of it. Adult Mo lives alone-currently still with his mom.
I’ve yet to see a post that says they are in HS explain how they can be in HS if Jian Yi is still here. Because if they were in HS Jian Yi should be missing right now. It says he disappears on the second day for years..