last day plan

Hi,

my return flight is 18:00pm in Osaka airport.
I plan to check out hotel at Kyoto and take train to Nara, Keep luggage in station then taxi to Nigatsu-do Hall then walk around Naromachi .
then take train to namba subway, (leave luggage at station?) , walk around dotonbori.
then back to namba subway take train to airport.
is too rush or too late to airport?

It depends on when you start your day and on your pace of travel. I recommend to plan to arrive at the airport 2-3 hours before the departure of your flight, i.e. leave Namba around 3pm at the latest.

So, if you start your day early and travel at a relatively fast pace, I think you should be able to fit in everything. But if you want to start your day late and prefer a slow pace of travel, then it is too much.

yes, too rushed!

If your flight is at 6:00pm, then you need to be at the airport at least 2 hours prior to that, i.e. 4:00pm

Another thing you need to bear in mind is traffic and unexpected events/delays if you don't want to miss your flight .

I would agree that it is too rushed. Since you need to be at the airport at 3-4pm. You need to depart Osaka 2-3pm. So travelling to Nara, back to Dotonbori, while visiting those places doesn't seem like a good plan.

For Dotonbori, casually walking around looking at food options and window shopping probably needs a 3 hour visit for a first attempt.

Nara should be an all day affair if you wanna see it all. So squeezing 11 hours for sightseeing into 5 hours isn't a good plan.

I'd probably just do something small in Osaka, then visit Dotonbori around lunch, then head off to the airport.

If you get an early morning start and finish all your packing/preparations the night before, you can see some places before your flight. Traffic is really not an issue if you are taking the train. As said above, you should be at KIX at least 2 hours prior to your flight.
If you have not seen Nara before, then definitely make a few hours for it. Concentrate on the Nara Park area - the Todaiji & the Great Buddha is the crown jewel of the area. Depending on your pace, you can fit in some other places, like Kofukuji, Kasuga Taisha etc. The places really don't take that long for each.

Dotonbori is great, but is by far better in the evening and you just don't have that option. If you still have a few days, go there in the evening after a day of sightseeing in Kyoto or wherever. For your last day, consider somewhere else that might make a better experience - going up to the top of the Abeno Harukas Bldg for example.