Since Miyoshimaru can break seals, it is probably true that he knows some magics.
Miyoshimaru gave Lord Fujiwara's son some silkworm eggs. He then, taught him what to do with them.
According to Lady Fujiwara's diary, he visited her in the shrine when she was sick. She also instructed him to seal the doors so the disease would not spread.
When Miyoshimaru got infected by the disease, he broke the seals of the Manor doors.
At the Shrine, he witnessed Lady Fujiwara eat her own son.
- All Miyoshimaru's notes are written in a leaf.
- Miyoshimaru's cause of death was probably the disease itself.