Opinions on my round-trip drive in Kyushu?

Hi. My girlfriend and I are gonna travel to Japan in May. We plan to rent a car in Kumamoto and do a round-trip around southern Kyushu. Idea is to see beautiful places and stop when we feel like it. The plan at the moment looks like this:

FRIDAY

Arrive in Kumamoto afternoon (from Osaka), stay overnight.

SATURDAY

Rent a car in the morning and drive to Yufuin, where we'll stay overnight. On the way stops to see mount Aso (if it's open), Kurokawa onsen (go to bathe), Kokonoe Yume Otsurihasi (and Yamanami highway).

SUNDAY

Start the morning with a Yufuin bath and drive to Takachiho Gorge (maybe row the boat) and drive all the way to Cape Toi via the coastal road for the views. Stay overnight somewhere in the South-East and drive back to Kumamoto on MONDAY afternoon to return the car and catch a train (or even a ferry) to Nagasaki.

My questions are:

A. Does it look reasonable time wise?

B. Is the coastal drive to Cape Toi worth it?

C. Does it look like we have use for the Kyushu Expressway Pass?

D. Would some other route be better? I'm quite convinced about the first part up to Yufuin, but not really sure what would be the nicest way back to Kumamoto.

Thank you all!

Have you ever driven in Japan before?

The reason I ask is that it's REALLLLLY slow to drive in Japan if it's not on the expressways, which covers much of your area (specifically around ASO).

Others may disagree, but I think you are trying to do too much in too little time. For example, Takachiho is half a day of 'stuff' just at the location.

I agree with mfedley, I think you're going to miss a lot, especially at Takachiho. The dance performance at the shrine is one of the main things to do there, but that's in the evening. Most people stay there overnight to see it.

How about skipping Yufuin and driving Kumamoto to Takachiho, then staying overnight there? That way you can explore Takachiho and see the shrine dancing in the evening, then you're a bit closer to the coastal road and Cape Toi there. There's a lot to see on that road, and it is very beautiful! I recommend staying in Obi, I thought it was a really quaint area with a lot of charm.

Then head back north from there.

We did something similar, but I don't remember the exact route at this point. We flew into Kagoshima and ended up in Miyazaki, and visited Kagoshima, Ibusuki, Kumamoto, Cape Toi and Obi, Takachiho, and Miyazaki City. We also had more time than you and were able to spread the driving out a bit.

Thanks for your replies! Would you say the Nichinan coastal road is nicer than the Yamanami highway (with Kurokawa and Kokonoe bridge etc)?

And to answer mfedley's question, yes, I have driven in Japan before but not much. And those times were in Yakushima and around Kaga-onsen.

I'm really looking forward to the Yamanaka highway (and Aso, Kuju, Kokonoe bridge, Kurokawa, Yufuin.) If it's either that or the Nichinan coastal drive, I gues we will choose the former. The route back to Kumamoto we have to think through.

Too much for 2 days.

Maybe arrive at oita (from Osaka) and drive straight to Yufuin. Give you an extra half day. And places to closer to most locations.

I think we'll do Kumamoto-Yufuin-Takachiho-Kumamoto, and stay overnight in those places and check other places that are on the way. The mileage gets halved.

Someone mentioned driving to Takachiho through Taketa. Is it worth the extra kilometers? I saw there's some singular sights like Oka castle ruins and Harajiri Falls, but other than that is the drive especially nice? Or should we rather drive more straight and possibly stop at Kuju flower park?

You can go to both, and they are not the same, but going from Kurokawa to Yufuin is a bit redundant.
Of the two, the outdoor baths at Kurokawa are really nice at some of the places (there are around 30, some are great, others are just meh). Try out some of the better ones - and you'll likely need to drive to them, so use the car.
https://youtu.be/Xs_JXC6bhkM

For Aso, the crater rim may be closed (highly likely, in fact), but with a car, there are loads of other great places to see as well - the Daikanbo Lookout is great when the weather is clear, plus the Nabegataki Falls, Kuju Flower Park (in fact, May is the best time to go there), the Yamabuki Springhead, etc.
https://goo.gl/RwpnU8

For Cape Toi being worth it, only you can decide. I wouldn't go all the way there just for that. But you can see some other good sights in the area, like Udo Shrine. You could also stray into Kagoshima to Kanoya City and see the Kanoya Rose Garden - May is typically when they really explode in color.
http://www.baranomachi.jp
Actually, it does strike me a bit odd why you don't mention Sakurajima. It really is impressive.

Yufuin is 40mins from Beppu/Oita. And 2hrs to Takachiko.

Why get a ccar from Kumamoto? 3 hrs to Takachiko and even more to Yufuin...

Thank you! The thing is, I'm sold on the Yamanami highway route, and Yufuin in the end of that sounds like an exciting overnight stay. And Kurokawa happens to be on the way, so I was thinking maybe a stop there for a nice outdoor onsen. I'm gonna add stops at Daikanbo lookout and Nabegataki Falls on the way. Thanks for those! Do you have any specific recommendations for the outdoor onsen in Kurokawa? I guess it's too much to ask to be able to bathe with the girlfriend in the same bath?

Kagoshima is too far for such a short time we have. I've seen Sakurajima from the distance before, when I went to Yakushima. It was smoking and did indeed look nice.

There are some mixed baths in Kurokawa onsen. But maybe those are not the nicest. This should be a list of 混浴　baths:

https://onsen.nifty.com/ft-konyoku/kurokawa-onsen/

Look out for 混浴　(mixed) and 露天風呂 (rotenburo) or 貸切風呂　(private). However I would ask if the privat option is a rotenburo. Sometimes it is an inside bath only.

Regarding nicest onsen in Kurokawa, I went to only 3, but would say my favorite was Yama-Mizu-Ki:

http://www.yamamizuki.com/sp/

Enjoy the soak.

Thanks a lot!