Getting there

You can get to this hike by either taking the Akechi Tetsudo Line to Akechi Station (change trains from JR Chuo Line at Ena Station) or by driving and parking at the free Taisho no Mura carpark (across from the Valor). 

Maps

At the trailhead there is a map

Route/Trail notes

From the carpark, walk towards the bridge on the right and cross it. Go down the street where there are some old buildings from the Taisho period. Continue past this street, on the road you should see signs that point you towards the ruins of Akechi Castle. Continue following these signs. It will take you up a hill. The track starts besdies the Roman no Kan where you enter the forest. Continue along the forest path and head up the hill towards Akechi Castle. You will pass a few shrines along the way. Feel free to stop at them. Also look out for bears. 

At the peak there is a bench you can sit at and have lunch. 

Follow the same path back. I recommend also taking a sticky beak at some of the museums along the way, they are somewhat interesting. 

Permits/Costs

Nada

Other References

Good luck finding any other information about Akechi Castle in English. If ever in doubt, use Google Maps!