Climb Mount Aso in mid december

I will be in Kyushu mid December. Is it safe to climb Mount Aso at that time? Will it be too cold? Can I proceed to Takachiho Gorge after Mount Aso on the same day? Will it be too rush? N then return to Kumamoto on the same day? Hope to hear your advice. Thank you

I assume you mean climbing to the Nakadate/Takadake summits of Mount Aso. Or do you mean just seeing the crater, which can be accessed by car or bus? I assume the former.

Is it safe to climb Mount Aso at that time?

It depends on the situation with respect to snow, weather, volcanic activity, your physical abilities and prepardness. But if the weather and trail conditions are fine and you are well prepared and able to climb some very steep mountains, then it is potentially possible. Unless you are experienced in winter hiking, you should not do the hike if there is snow.

Will it be too cold?

If you bring proper clothing, it will not be too cold. This question makes me suspect that you have very little mountain experience and you may better not climb the mountain, especially not in winter.

Can I proceed to Takachiho Gorge after Mount Aso on the same day? Will it be too rush? N then return to Kumamoto on the same day?

And where will you start the day? In Aso? Kumamoto? In any case it seems a lot of driving and very little sightseeing. Potentially possible though, if you start early in the morning. Probably impossible if you travel by public transportation.