Sunshine 60, Haunted Skyscraper?

It is said about the Sunshine 60 skyscraper from Ikebukuro, Tokyo, that it is haunted, because it was built over the site of the old Sugamo Prison, where numerous executions took place. Also, this was the prison where several Japanese personalities from the World War II (including Hideki Tōjō, prime minister of Japan) were executed, convicted as war criminals by the Military Tribunal for the Far East.

It is said that supernatural sightings were reported in and around the building...
I stayed in Sunshine 60's observatory late in the night, taking photos, but the only ghosts I saw were... the window reflections...