Asahidake-Kurodake 1-day hike in August

Hello, I plan to visit both Asahidake Onsen and Sounkyo Onsen in mid August and would love to hike from Asahidake to Kurodake in 1 day (Daisetsuzan National Park).

I'm reasonably fit, but not an expert hiker.
How physically challenging is the hike in summer, and how long does it take?
How frequented is this hike, can I expect people to disappear once I leave the ropeway's vicinity, or will I have company all the way? Which leads to my next question: What about bears in this area?

Thank you.

Also, if anyone else wants to do this hike in August and is looking for someone to go with, send me a message.

I'm reasonably fit, but not an expert hiker.
How physically challenging is the hike in summer, and how long does it take?

The main challenge is the length of the hike. You need some stamina to do it in a single day. But the trail itself is not very challenging, and there are no difficult passages that require special hiking skills. The only slightly challenging section is the descent down the back side of Asahidake which is very steep and is slippery. Hiking sticks come in handy there. But apart from that section, it is all relatively easy walking.

According to maps it takes about 7 hours (not including breaks). I personally usually walk 30% faster than that on plains and descents and 50% faster on ascents. I probably hike above-average fast, but I think you have to be a rather slow hiker to require 7 hours.

How frequented is this hike, can I expect people to disappear once I leave the ropeway's vicinity, or will I have company all the way?

On weekends and holidays (I think most of August, really) with good weather, you are likely to meet many people along the way. As the weather gets worse, people decrease. Between the Asahidake and Kurodake peaks, the crowds are smaller, but there should still be quite a few other hikers.

Which leads to my next question: What about bears in this area?

There are not many sightings, and I have never heard of any incidences. The top station of the Asahidake Ropeway provides information about eventual sightings.

Thank you, Uji, for your very detailed and helpful answer. 7 hours sounds very doable from past experience. I'm glad there are likely to be other people and not too many bears. Would you have any tips for where to obtain a map for this hike? Thank you!

7 hours sounds very doable from past experience.

Remember that is the time maps give without breaks. Also make sure to check the business hours of the chair lift and ropeways.

Would you have any tips for where to obtain a map for this hike?

I love this one:
https://www.amazon.co.jp/dp/4398762639/