Foreshadowing??

Masato's ex is a friggin bastard that played with Masato's feelings and at the end left him, raped and hit him. No I do not think Naru is going to like him ( I think you really didn't read the manga properly)

In Sayonara while Masato is messing with the main couple I do not get a bad vibe from him. While reading his story and seeing how awful his first love is (he left him without hesitation, raped and hit him) I think that a) the mangaka did a great job presenting him like that b) deep down he does not meddling in couples for fun, he genuinely thinks that gays and straights cannot work. And I really don't think that a casual acquaintance can make you split with someone if the relationship is good. I really liked the story (all 3 mangas really) and I really like Asahi (as much as I like Iku and more)

I did read the manga properly, and I'm not saying this to ruin the manga or anything. I love Love Nest and I find it to be my most favorite work out of all of Minaduki Yuu's works. I know that Naru "oversees" all of his tenants but there's that cliche in BL mangas that the ex comes back. Yes, Masato's ex is a horrible person but Masato needs to find closure or else I feel like the issues in Masato's backstory won't be resolved. Asahi has already met his ex-wife and by meeting her the mangaka's not creating angst or anything, I believe she appeared to show that Asahi has overcome his past. The same goes for the couple that Masato "ruined" (a.k.a Asahi's younger brother). It's shown that the couple has overcome Masato's interference and has gotten stronger. These kinds of traumas or issues that are in each characters backstories should be resolved in some way in order for the story to progress and the readers to feel content. I believe this manga is still continuing, and therefore Masato's ex may show up. But then again, I may be wrong.