Sleep over at domestic haneda

I will fly from sapporo and arrive haneda domestic airport at 0.25

Can I sleep over the domestic terminal?
(I heard that the airport will close on 2 am. but not sure)

In the case that I can't stay there
what should I do? How to go to International terminal?

Can I sleep over the domestic terminal?

No.

In the case that I can't stay there
what should I do?

Stay at a hotel or in the international terminal.

How to go to International terminal?

I think taxi is the only feasible method at that time of the day.

I found this blog.

http://arapid86.blog86.fc2.com/blog-entry-53.html

I'm not sure if I understand it correctly or not
since I can't read japanese much.

Does it said that I can take a bus no.16 at first floor to the international terminal?

*********Beginning of quote (or translation from the blog)*****************

"After arriving at Hanneda on late-night Skymark flight

The flight from Kita-kyushu to Haneda mentioned earlier arrives at Haneda at 1:10.
Of course no public transportation is available, and you cannot sleep over in Haneda No. 1 Terminal due to security.
Because of that, the following notice is provided prior to departure.

(The notice)
To passengers on late-night flight to Haneda

- After arriving at Haneda, you cannot wait till the morning inside the domestic terminal.
We ask for your cooperation that you will move to your accommodation after your arrival.
- If you have any connecting international flight, please inform our staff before departure.
You will be able to use a free shuttle bus after arrival (board from 1F, no. 16 bus stop).
This bus runs only one-way from the domestic terminal to the international terminal, only once.
- All public transportation will have stopped for the night, so if you need a list of taxi companies, please inform Skymark ground staff.

This notice was distributed in Kita-kyushu airport.
I searched around on the internet a bit, but it does not seem to be widely known that there is one free shuttle bus late at night.
As the international terminal is open around the clock, it is possible to wait for the first train in the morning there.
(I did it once, but I will never do that again!)

This time, I moved to the international terminal, took a taxi to Otorii, and stayed over at Toyoko Inn.
Taxi cost about 1,600 yen, hotel 5,000 yen. In total, there was no (cost) advantage vs. taking the Fukuoka flight."

************************End of quote****************

Toyoko Inn Haneda Kuko 1 is located near the Otorii station.

Thank you for translation.

I have no connection flight
I just want to wait for the train
can I still use shuttle bus?

If not, domestic terminal has taxi in that time?

I came back from the trip.
After got off the airplane
there was a shuttle bus waiting in front of terminal 16. There are many people sleep ove at the international airport on the bench.

is it cold to stay overnight at the international terminal building in winter? will be arriving at haneda airport in one week time, also quite late at night.

It's warm enough to get some sleep but about 3 am. I feel a little bit cold I guess they close a heater for a while. There are a shower room and resting room in 2 floor.

Thank you Rose for the feedback. This is very useful!