What really disappointed me was that I actually loved the story regarding Alexi's parents. I actually bawled like a baby during it, and I thought it was a nice addition to this story. But since it was so... explicit in its portrayal, I was hoping the same would apply for the main couple's. After seeing the parents', I expected our couple's to MOVE somewhere. To develop beyond friendship.
And I wouldn't have minded if it was just friendship if the manga didn't have a bloody "shounen-ai" tag on it. So I wholeheartedly agree with you that it seems a bit out of place in its genre, and for that, lacked a lot of closure. I also didn't like how ambiguous they made Gil's and Floran's relationship. The author could have clarified that it was nothing more than a friendship, as they did (for the relationship) during the arc with the parents' love story, but they didn't. They treated it with the same atmosphere delegated to the main couple, which made me start questioning the main couple's attraction as well. ;;
This story had a pretty original concept and very cute characters, but in my opinion it really lacked in closure.
I like shonen-ai / slow-paced stories / "shy" relationships (like "Senpai" from this author, which a beautiful piece of work !) but this was more on the bromance side rather than the romance one. You can guess the partners really care for each other, at some points the author might be hinting that it could be a little more than friendship, but nothing more.
HOWEVER, while the same sex pairings stay in the friend zone, the two heterosexual couples in the story get to have their very own love story... Alexi's parents, obviously, and then the couple in the last chapter (that I didn't fully read because I'm not really into shoujo...) in which the girl even gets her sweet love confession...
Seriously when you read something labelled as "shonen-ai", this is kind of frustrating.