We're aware that some users using the latest developer beta iOS 12 are experiencing the issue with the manga viewer.
This issue is permanently fixed on iOS 12 Beta 3 and later. Please kindly update your iOS version to solve this issue.
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: Jul 11th, 2018