Yeah. Even at her most emotional moments, Sarasa never let her feelings for Shuri affect her judgement. Even though learning the truth almost destroyed them both emotionally, she's the one who was able to come to grips with it. If anyone was swayed or ruled by romantic emotions and reduced to supporting on the sidelines, it was Shuri, but even that is overstating the case.

The thing that makes Basara my favorite shoujo ever and second favorite manga ever is that, from beginning to end, no matter what Shuri went through or what turns the plot took, it remained Sarasa's story. (Though, I still need to read the last 2 volumes of short stories...)

I don't think it's really that Sano's angst was the cause, but rather that all the problems started cropping up when that arc started.