Takahiro is supposed to be in the Junjou Mix chapter in the 8/30 Emerald issue so hopefully the storyline will make some progress and they'll finally tell him (since the sister-in-law has figured it out anyway)
It's the style of this mangaka from what I've noticed. She finds a formula and she repeats it ad nauseam. It's why I didn't bother to read Sekaiichi Hatsukoi. It seems to be the same deal according to the comments and the bits I have read complete with the ol seme interrupting the uke with a kiss when there finally may be progress. Both covers feature a sharp eyed seme with a dinner plate eyed uke with his mouth wide open as if he is about to catch flies. Oh oh oh and nearly every guy who meets the uke wants him and wants to break up the relationship. And they all just so happen to be hot, single, and well off.
And before someone obnoxiously asks me why I read this I'll answer ahead of time: I am not a psychic. I had to read it to see if I would like it. So I did. And for a while I did like it until the author decided to go in circles. Lesson learned so I skipped her next work.
The story is more and more repetitive now. The issues they have in mind are the same all along. I really wish that the chapter in which they tell Takahiro about their relationship will be released because it's the only reason why I continue to read this manga.