Getting there

Trust in Google maps. Put Suwagane into Google maps and it let it take you to the sleep town of Akechi. Turn into Akechi no Mori. You will see a yellow sign that points towards the trailhead in Japanese on your left. Ignore this sign and keep turning straight. If you go up that way, I am sure that you could get to the summit, but the road is very narrow and basically impossible to pass in a car. 

Follow Google maps and you will reach a gated road with a no entry sign. Ignore this sign and continue on driving. This will take you up a narrow forest road. At the top of the hill you will see some blue traffic cones with the parking symbol on them. Park here and you will find the trailhead right next to it. The trailhead is chained off and looks like it is an old forestry road. 

Maps

Route/Trail notes

There are multiple trails that you can take. Just be warned that the tracks are not well maintained and some of the bridges are of questionable structural integrity. 

From the trailhead continue straight and follow signs for the summit which are written in both English and Japanese. In about 10 minutes you should reach the summit. From the summit you can see Aichi Prefecture in the distance and faintly the ocean. 

From the summit you have a few options. You can head back to your car or continue onto another trail. The other trails will take you to the base of the mountain which you can then reascend and drive home. I personally haven't done these other trails so I am not sure about them. 

If going back to your car, follow signs for the community centre. As you do this, you will reach another junction. From this junction follow signs for forestry road as this is where you parked your car. Be warned that there is no signal at the top of Mount Suwagane and if you get lost (like I did), you are basically stuffed. There is also definitely bears on the mountain. 

Permits/Costs

Do you need any permits? What's the cost?

Other References

How can I find more info? Any guide books?