This is due to the fact that Manga Rock was previously removed from the Play Store because of objectionable content. After a long time appealing with the Play Store review board, we were able to get the app back on store and in order to reduce the risk of the app being removed from the store, we have to take down these following genres:
We hope you understand in this matter and we suggest you check out Manga Rock Definitive version to continue reading these manga genres.
Step 1: Go to your device settings > Security > Turn ON "Install from unknown source"
Step 3: Install the app
Step 4 (optional): Restore your data from backup on Manga Rock Cloud