Hear me out, Saku-chan was promoted to being HKT48 member on 4th March 2012.
Now, look at what date we have now, coincidence?
As for how it was in the past it looked like longest contracts were like 12-13 year long, or at least some members stayed for this time in AKB48 itself/or in sister groups.
But times are changing, and now if you look at Chinese side of story - SNH48 members of 1st generation graduated in October 2020.
But why would I point that out here? Well, it's because 1st generation of SNH48 started in... 2012!
So what if we have here similar situation to what Kiki (Xu Jiaqi) had when she joined the survival show, was a finalist and won a spot in the group, but during her time in group The9 her contract with SNH48 was coming to an end. Of course, here she decided to renew with the agency owner but what if Sakura had a similar situation and she decided not to sign a new deal with a Japanese company?