Is half a day enough for Wizarding World?

We're scheduled to arrive at Kansai airport at noon. The Universal Studios website say it'll close at 6pm the day we're arriving, so I was wondering if it's possible for us to squeeze in Wizarding World in four hours. Should we buy an express pass just to be sure?

6pm sounds like a very early closing time! I was 10pm on a weekday when I was there. It is possible if you only went to the Harry Potter area, and an Express Pass would certainly speed things up. However, the Express Passes sell out very early so unless you buy one online (other discussions on this forum can tell you how) you won't get one.
You could also save time by purchasing your Universal Studios entry ticket at Kansai Airport. They do not sell Express Passes, though.

6 p.m. closing on two Fridays seems weird. Maybe they have a private function planned those nights.

But half a day is enough, if not more than enough, for Harry Potter. Mostly you want to look around, ride the Forbidden Journey (and how can we be allowed to ride it if it is forbidden?), and get a mug of butter beer. Forget the shops unless you want to wait a half hour or more just to get through the line into Evanders, or pay $18 for a small box of jelly beans next door.

We had a great time there last month, but I can't think of any reason to go back.

Buying advance tickets and express passes online is not too difficult. Search for Blood Princess's explanation of how to do it.

Was there last year! It was fun!

However you might need to get timed entrance into HP.

Then shops are very very busy. The wand shop had a line for 1.5 hours at the time. We couldn't even ride Forbidding Journey as the line up was almost 3 hours but the walk through of the Castle was only 1.2 hours, so we opted for the walk through. Was very cool inside.
Had lunch at broomstick, but still about 1 hour wait. And Hot Butterbeer and Cold Butterbeer so good!!

For the sights and sounds, a few hours should be good, but if you want to ride a ride, probably not enough time. We were in HP area for almost 5 hours before checking out the rest of the park.

Hope this helps!!
Have Fun!!!

Thanks for the responses guys! :)