As the article states, this is a sequel to 1994's Menkyo ga nai!, with Hiroshi Tachi playing the same fictionalized version of himself as in that movie.
Just to mention a few possible clues, Xu Meng met her ex bf through a magazine, and he mentioned she had other…
Wow, aside from the detail about Xu Meng's other penpals, I never noticed any of the other things you mentioned! I might have to rewatch some of the previous episodes of this show, as now I'm wondering if I missed any other details...
I recently re-watched the episode of Hello Saturday where the actors were promoting this show and I noticed that Song Xiao Ying Zi describes Xu Meng as Qiao Suqing's friend. So far we haven't seen anything to suggest that they knew each other, but I've seen comments here highlighting the parallels between them (most notably caring for abusive old men), as well as a theory that Qiao Suqing might have been one of Xu Meng's pen pals. Given all of this, I wonder if Qiao Suqing knows anything about Xu Meng's disappearance or, assuming Xu Meng is the one who killed her father, if Qiao Suqing is in any way involved with that.
As the article states, this is a sequel to 1994's Menkyo ga nai!, with Hiroshi Tachi playing the same fictionalized version of himself as in that movie.