Very little was known about her, since she was only mentioned in chapter 170 when Hayato, Miu and Kenichi visit the Fūrinji family grave.
The official guidebook gives a few more details about her in Saiga’s and Hayato’s profiles.
- Shizuko was of Russian decent and Saiga inherited his blond hair from her.
- Saiga’s exceptional teaching skills are not due to Hayato’s genetics, but a result of his mother’s influence.
- Hayato was already very advanced in age when he and Shizuko met and got married.
Therefore all that can be said about her is that she had blonde hair, was a great teacher, and that there was most likely a considerable difference in age between her and her husband as she was still young enough to have children.
It is unknown when exactly she died and what caused her death. Since she was not mentioned during the Kuremisago conflict it is to assume that she had already passed away at that point and that Saiga had lost his mother at a rather young age.
No information is given about whether she was a martial artist herself.