In regards to Toshiro, I'd like to point out a few things:
1. Why would Kenji's death be considered breaking news? He was a poor guy from what I recall, and aged. Heart attacks would not be completely unexpected.
2. I know Toshiro is intelligent, but I believe that him jumping to the conclusion of murder through the notebook is a bit far-stretched. Again, for all anyone (besides Hisako) knows, it could have been a normal death.
3. Wouldn't Sasori's death raise a red flag to just about anyone? And if she's a detective, how could her name not be an alias?
4. How did he learn Sasori's name in the first place?
Please don't take offense to this, but these points seem important to elaborate on.