From Haneda to Osaka night bus

Hi,

I will be arriving at Haneda airport about 10:30 pm, and it will be estimate 11:30 pm to settle the immigration process.

So I wonder is that possible to take night bus from Haneda to Osaka??
what is the last bus depature from Haneda to Osaka??

nope

No such night bus.
http://www.haneda-airport.jp/inter/en/access/bus.html

There are buses departing from Yokohama at 24:20 and 24: 40 from Yokohama station and Shinjuku,
but there are only Japanese reservation forms, you cannot book on the day night.
A bus that can be reserved in English departs at Yokohama station at 24:05,
but no enough time you may not reach there and don't know your travel date, it may full already.
http://willerexpress.com/en/

So, no recommend such risky plan, you should change flight ticket "for KIX", if possible.
https://www.kansai-airport.or.jp/en/access/train
Or, change flight ticket to earlier arr one.

It's a 9 hour bus. I would highly recommend flying or taking shinkansen train.