The whole thing since like 200 chapters ago I think had been flashbacks, is their school memories, I don't know or remember much about he tian and mo's future or present you could say, but when It comes to the other two, after school they will stop seeing each other, they will reunite after some years, the four of them basically drift apart after school
I’ll also remind that there are pple who‘s reading 19days since 2014 and to be honest if this story reaches 800+ ch. it won’t surprise me anymore, that’s the concept of slow burn. Anw for the plot it’s currently our boys middle school life flashback until Jian Yi will disappear (we’ll be back to the present that time), so the four will be separated for a while until they’ll meet again. What is confirmed is both couples will be together in the future
If you want a detailed explanation, here : https://zhanxixis.tumblr.com/19daystimeline, hope it helps
ngl I’ve been reading this for almost a year now and i have reread it from the beginning twice and even so, I’m started to get more and more confused over what exactly the plot and purpose of this is. don’t get me wrong tho, i still thoroughly love this , I’m just starting to wonder what’s happening