View from my office, abandoned castle ruin of 11th century

There is a small hill in front of my office and at the base of the hill, I can see old monument by the road that nobody notices.
Writing in the monument is hard to read due to wear and tear except the name of the place that says "Ruin of Shidu Castle".

There used to be a small castle on top of this hill in 11th century.
History says it was built in the year 993 by Tomosuke Fujiwara from a noble clan that leads to Tokugawa family of 17th century(...I doubt it).
The castle was abandoned in 17th century they say.

Then time passed and people here decided to build a Buddhist temple on top of the hill in 1950's.

However it was abandoned again later and only this monument and small temple building remains on top of the hill now.