
A page seems to be missing after pg 38 chp 4

I believe the artist did that on purpose to save drawing an needless panel, since it's implied from the previous page that Arito was going to introduce himself. And on that page you're talking about, in small text off to the side in the bubble its says "So you're Arito-kun," which does imply that Arito introduced himself "off screen."
I'm a little sad the disease is gonna die he didn't even know his purpose and people kept attacking him.