We're aware that some users using the latest developer beta iOS 12 are experiencing the issue with the manga viewer.
This is a confirmed bug caused by Apple's latest operating system. Our Devs are carefully investigating further and we hope to fix it as soon as we can.
We truly apologize for this inconvenience caused and thank you for your understanding.
Affected version: All devices that have updated to iOS 12
First reported date: Jun 6th, 2018
Resolved date: TBA