It looks like the author made this as extended epilogue to the prequel but nope, they just weren't capable of bringing the story forward, they made the 2 get closer, introduced a love rival and made some cliche chapter.
The love rival is just sad, appeared to suffer, is clear that it was made for more plot but the story got axed or the mangaka dropped it off.
Could have even used a few more chapters in the office to couple the cool guy with glasses girl and make us the female boss decide to search for a companion too after seeing everyone around getting hitched.
It was a uneeded extra.
And the cover was made to make people turn around, giving the heroine boobs.