Osamezuka sits in the same Sakai cluster as its larger neighbours, a small mound whose occupant nobody names with confidence, since tombs of this size are remembered by their shape and position rather than by a story. The city around it has plenty of story to make up for that.
Sakai was, for a few centuries, one of the great merchant cities of Japan. In the fifteenth and sixteenth centuries it was a free port that ran its own affairs through a council of wealthy merchants, defended by moats and mercenaries, trading with Ming China and later with the Portuguese. The Jesuit missionaries who visited called it the Venice of the East, and the merchants who prospered there turned their money to the arts. The tea master Sen no Rikyu, who shaped the Japanese tea ceremony and served the warlords Nobunaga and Hideyoshi, was born in Sakai, and the city still has a strong connection with tea. A sweet and a bowl of matcha in a local tea room is a very good use of a rest.
The tombs are older than all of that by a thousand years, and the combination makes a good portrait of the region. You pass a ditch full of lotus leaves, a pine-covered mound, a temple, and a convenience store, all in the same view.
Riding here, the main matter is patience. The southern Osaka plain is flat and dense, with grid roads and many lights. The ride list leads to Yamada-dera, the temple site in the Asuka region of Nara, where the old Yamato kings and the first Buddhist temples stood, so you ride from one ancient landscape to another and cross the Kongo hills on the way. The roads over the hills are curving and shaded with cedar, and the temperature drops several degrees on the high ground. Spring blossom and autumn leaves are the high points.
Fuel is easy in this part of Japan, and Sakai has stations on every major road. Bring cash for small shops, and keep rain gear handy, because the weather can turn quickly.