Hmm, so what's the big secret? It would seem like he was lying and using her for his own ends this whole time, and with all of Ririchiyo's trust issues, that's certainly what she's thinking at the end of the episode. What she saw in the hallway when she went to visit him will help that misconception. It's too bad we never saw what her text message said.

But if I had to guess from the preview...it would be that Miketsukami was actually the one receiving her letters when she was young. That would be how he "saved" him so long ago. He might even be the one who she's actually engaged to, but for whatever reason, he asked Kagerou to take his place.

I'm a little saddened by the fact that we will probably not be seeing her sister any time soon, if at all. That was always the most promising aspect of this story for me. Maybe the manga covers it...

P.S. And oh yes that mother (9:19) was an "S", ku ku ku.