I appreciate how Arata serves as a lens for the Sabu to depict the impact of Yuzu and Mei's relationship, highlighting their personalities and unique style of love through their influence on him. It also gives us insight into their strength as a couple, which is being tied to this school project.
The merger feels like that one final opportunity to showcase the strength of their relationship, so it makes sense that it leads into their marriage timeline-wise. They're already acting like a confident married (but busy) couple. Also, really loved that last page.