Honestly, now that think of it, I believe it'd be an awesome plot-twist if, in the next chapter, it was revealed Miku was actually faking all of that and it was all her plan to get her sisters temporarily to help her. That'd make her even sneakier than Ichika.
And then, to top it all off, when it seem like we've seen it all and Miku is about to win, Yotsuba goes for the kill and kisses Futarou, once again leaving everyone with their eyes wide.