Plausible scenario: When university rolls around, Hisao gets fed up with Emi's inability to take adult life head-on (keeps skipping class, wastes money impulsively) and they mutually break up. As uni graduation nears, Hisao finds out that some paperowrk from Yamaku never made it to the registration office, sending him back to the small town. He has a chance meeting with Meiko and the two hit it off. They reminisce and both realize how much Hisao has grown up and how much more easily they relate to one another. The conversation accidentally becomes too personal and Meiko makes an excuse to leave, but not before Hisao can get her contact info.
From there, any number of evens can lead to Hisao plowing like a farmer
All the lovely Meiko, less of Hisao being a needy little shit.