Yeah, if you could report this issue to them, it would be great. Here's the more specific response that I got:
Hopefully if they see at least one other person with the problem, then at least they won't think it's an isolated incident regarding my "network environment".
Edit: Oh yeah, they'll probably tell you to restart the app, restart the phone, and delete the app... so try that first and then mention it if it doesn't work.
Also, I love how Japanesey their responses are.
Okay, I realized that, since transferring my EN LL over to my iPad, I hadn't redownloaded the Pure Nozomi story yet. I am also having this exact 50% issue. In fact, it's acting differently than downloading other ones; other ones kind of increases the % (e.g. 11%, 23%, etc.) and then finishes. The Pure Nozomi one immediately goes to 50% off the bat and then immediately fails and then reboots. So I think it's everyone.