After Kurumi's initial plot and attempt to manipulate Sawako out of her way so that she could have Kazehaya to herself pretty much fell on deaf ears, it was plain to see the gears turning in her mind for the remainder of that episode until she settled upon a new plan - Trying to shift Sawako's attention in the direction of Ryuu.
Of course, while Sawako is receptive to basically any advice thrown her way, getting her to think about Ryuu over and above Kazehaya is pretty much asking the impossible, so once again Kurumi finds herself at something of an impasse. However, with Sawako at least taking on board the concept that talking to Sanada might not be such a bad idea, it still gives her some elements to work to her advantage - Elements which become all the more potent as we receive another reminder that Shouta is actually quite the jealous one when it comes to these things.
Thus, as this twelfth episode progresses, so Kurumi's behaviour becomes borderline stalker-ish, as she tracks down Kazehaya's whereabouts at the on-going sports festival, plants a note purporting to be from Sawako in Ryuu's locker, and points Sawako in his direction to ensure that they meet at just the right time for Kurumi to break it to Shouta that Sawako is more interested in Sanada. A cunning (albeit slightly convoluted) plan, but is it going to work? Who knows, I don't have time to think about that right now while my blood is still boiling from Kurumi's behaviour.
Luckily for Sawako, she has at least one powerful ally on her side in Yano, who already seems to have figured out exactly what is going on with regard to the Kazehaya-Sawako-Kurumi love triangle, and even realises that a lot of the rumours floating around about herself and Chizuru earlier in the series originated from Kurumi; knowledge she has little hesitation in letting Kurumi know in her own subtle way. This is probably the best single exchange of the episode - Utterly bitchy and sly on both sides of the conversation, but compellingly realistic as I'm sure we've all seen or known girls who are masters at operating that way.
Anyhow, all things considered this was a wonderfully weaved episode which brought out the best and worst in all of the major characters - We get a glimpse inside the heart of Ryuu (as if we didn't already know what was to be found inside), a good long look at the "real" Kurumi, a reminder of Kazehaya's jealous streak, a great view of Yano's social nous, and of course the usual blend of naive innocence and determination from Sawako. All of this blends together to serve as a great reminder of why this series works so well - All of the major characters are strong in terms of both personality and the direct effect they have on events, which makes it far easier to be drawn into their trials, tribulations and fun times until you don't want the episode to end... something which is particularly true on this occasion as we're left with something of a mid-season cliff-hanger.