Wow -- I could have sworn I've read it - or maybe I wanted that kind of story so bad I made one up but I don't think I'm that creative. Something about Jinx-san and architect-san being forced to hang out by their bosses on a project at Jinx-san's house, and them connecting over a garden.... maybe I'm mixing up the stories but pretty sure there's a one-shot out there with that couple.
Hm... This one isn't the sequel -- but it's SUPER GOOD and has a rather nostalgic feel -- I'll keep looking but maybe you'll like this one in the meantime :) http://www.mangago.me/read-manga/kimiiro_eden/
i still hope the editor-san can persuade sensei to make nii-chan and jinx-san story cause i really really really need their story gaawddd