Dear, i will be arriving late to kansai airport at 10pm. By the time I reach, all JR exchange office will be closed. I will be directly travel to Amagasaki. If I want to exchange my JR pass around Amagasaki next day, where is the nearest exchange office I can go?
The Kansai airport JR ticket office is open until 23:00 (11pm).
You should be fine, but if for some reason you cannot make it in time, you can exchange the next day by making a quick trip to Osaka Station (Ticket Office (Central NO.12,13).
I hope this helps.