
This chapters seems to suggest He Tian went away during, or after, his 3rd year of High School. I don't think it's been explicitly said how long it has been since then, but I'd wager around the 5-year mark at minimum; XiXi went to college after HS, and seems to have already finished it by our current (future) timeline.
The first couple, Jian Yi and XiXi, also didn't progress much because Jian Yi was kidnapped and did not spend HS alongside them. Although Jian Yi came back *before* XiXi finished college, and thus before He Tian himself had come back, it's kinda impossible to say when exactly that was. I'd say for them it was about a 6 years (or more) gap, but we still don't know what happened pre-kidnaping that could have affected their current (non-existent) relationship status... but plot reasons aside, it still sucks how little they've developed after so long
I think it feels this slow for them because Old Xian wants to focus on TianShan for now-- so even when they show up, nothing much happens

KIND OFFFF? because the story started with older jian yi who finally got back after missing for so long. like xixi said, his childhood friend went off the grid during highschool, and now he’s back. i don’t know if flashback and retelling will be the right word to call it, but yes, it’s kind of getting a glimpse of the past how these 4 became friends and how 2 of them went missing for years

It seems like he comes and goes and leaves Momo for long periods when they're older (probably fully involved with his brothers/family mafia business). Hence why Momo always gets upset when he pops up out of the blue because he misses him so much. And just when they settle back into their routine He Tian will have to leave again for who knows how long. Then Momo just has to wait for him all over again.

i was just discussing this with another commenter. so when jian yi went missing during their second day of highschool, he didn’t come back until zheng xixi was in college or at least applying for jobs right? because he tian was with him, and he tian just got back in the story in this current timeline, and momo was already working and zheng xi applying for jobs. am i understanding this correctly?

The other commentar may be me lol but when Jian Yi comes back, XiXi is still in university-- there's a line where Jian Yi mentions studying hard on what he missed from High School so that he could go to the same uni XiXi was in. Then, in the "current" future events, XiXi is applying for jobs; so I think it's fair to assume that some time passed and He Tian showed up way after Jian Yi did. Momo specifically has probably not pursued higher education, and just has been working since finishing high school.
I'm so confused with this time skip. Someone please help me explain.
From my understanding, at one point he tian left and now he's back after how many years.
And it didn't even look like the first couple had any romantic progression which sucks