[X] Oh! Oh! Yuma read about romance in a manga once! Research suggests Big Sis should act mean and grumpy around Sayaka, constantly call her names and beat her up, and then blush while glaring slightly to the side.
-[X] Preliminary analysis has shown that Sayaka's brain's protective bone structure is too solid and difficult to penetrate, though Yuma doesn't quite understand what that means. The point is, Big Sis Kyouko asked Sayaka to marry her, and Sayaka did not even react! Clearly, taking this slowly won't work.
-[X] Indeed, Yuma must conclude that Big Sis Kyouko's approach of sitting by and doing nothing is equal to sitting by and doing nothing, which will get Big Sis Kyouko nothing but her butt feeling comfortable. But only if she's sitting on something comfortable.