From the City of Osaka, the Osaka Castle Museum and the National Archives of Japan.
Hideyoshi made Tokugawa Ieyasu serve him in 1586. He then attacked the Shimazu family of Kyushu and destroyed the Hojo family of Odawara, and unified the country.
In 1590 he ordered Ieyasu to move to the Kanto region.
In 1580, when Himeji Castle was given to him for his campaign in western Japan, he built a three-story keep there.
The site was first the Ishiyama temple of the Honganji sect, founded by Rennyo. It burned after an 11-year war with Oda Nobunaga, and then Hideyoshi began to build a castle fit for the ruler of the country.
Work on Hideyoshi’s Osaka Castle began in September 1583. Few records remain from that time, so its full shape is not exactly known.
The castle was praised as “unrivaled in the three countries” and “the strongest in Japan”.
After Hideyoshi died, the castle fell in the Summer Siege of Osaka. When the Tokugawa shogunate rebuilt Osaka Castle, it buried Hideyoshi’s castle under a thick layer of earth.
The walls and moats of today’s Osaka Castle were all built by the Tokugawa shogunate in the Edo period, in three stages from 1620 to 1629.
In 1984, a dig found a stone wall from Hideyoshi’s time. It can now be seen underground at the Toyotomi Stone Wall Museum. The present main keep was rebuilt in 1931 with money given by the people of Osaka.
There is no single right answer. Talking it over with someone at home is a good way to learn.