Since the 1.0.3 release, SekaiCamera stopped working on my iPhone. A couple days ago I sent in an email to the support staff to ask if this was related to my location (outside of Japan) and the recent update and I got a fairly quick response. Very nice, SekaiCamera!

Thank you for using Sekai Camera.
We thank you for bringing attention to this phenomenon.

Our survey has revealed that this problem is being caused by a bug in
our system.

We will attempt to fix the bug as soon as possible, hopefully within
the next week or two.
We anticipate that you will NOT need to download a revised version of
our application.
Moreover, we apologize that you (and everyone else in your region)
will not be able to use our app in the meantime, and appreciate your
patience and continued patronage.

--
Sekai Camera Support Center
support@sekaicamera.com

So that confirms it. If SekaiCamera is not working on your iPhone since 1.0.3, looks like a fix is on its way. Hold on tight, AirTaggers!