It wouldn't surprise me to learn Yumi wasn't even attacked and she's just trying to get into Shiori's head to explain why she turned her head.
And I have to agree. This is a boring case, which tells me the real pay off is going to deal with Kuroda; it might be a reveal of what happened with Amuro and Akai instead, but I think that's going to be saved for when we confront Rum. On top of that, it looks like Aoyama's fallen back into old habits - sacrificing the suspense and mystery of the case to develop the plot. As such, I'm seriously hoping I'm wrong about this one. Plus, really? A plain-as-day euphemism? C'mon! You were clever with Gin and Vermouth. You were classy with Takagi and Satou. Why this boring, blatant stuff with Haneda and Yumi?