You can tick this site very easy, or you can go tryhard. The easy version would be to take the train from Osaka to Mikunigoaga station, cross the road and take a picture of Genemonyama Kofun. Done.

Me, on the other hand, I went tryhard. In honour of the legendary Iain Jackson, I panned to visit over 50% of the components, even though after seeing a few, there is little reward in seeing more.

Furiuchi cluster
I left my family in Osaka and first went to the Furiuchi cluster. From Osaka I took the train to Hajinosato station, started with the one north to the station and then walked all the way down the cluster, ending at Furiuchi station. I covered 19 components along the way. Way more than necessary, but at a certain point my competitive streak kicked in. There is really not much to see. The bigger ones have some kind of medieval water trench around the mound. Those bigger mounds are completely covered in forest. They are all not accessible, but I doubt there would be something to see besides trees. The smaller ones are naked mounds or with a few trees on it. Nabezuka Kofun just next to Hajinosato station can be climbed. The rest is fenced off. It felt weird to cover this cluster, as most mounds are entirely within the suburbs, between houses. Without any knowledge about the existence of these Kofun, I would have probably mistaken them for unused patches of land, where construction of a new house will start soon.

Mozu cluster
Because several kilometres in walking with about 40 degrees and burning sun was not enough, I drove back to Osaka and took another train to Mikunigoaka station. Unfortunately you have to take the detour via Osaka, as there is no direct train line between the clusters. I walked the loop around Daisencho (probably the main component of the WHS) and Daisen Park, covering anther 19 components. This cluster is actually nicer to walk, as most mounds are in or around the park. There are also parking lots around the park in case you arrive by car.

In terms of what you can see, there is not much difference between the clusters. If you are limited in time or not willing to look at earth mounds for the better part of an entire day, I recommend the Mozu cluster. The park is nice, offers more shade and there is even a Japanese garden.