I took a glance at the raws for the published manga, and it looks like it's largely it's own thing within the setting (featuring all the Von Trapp characters we already know + some new heroes), so I'll be leaving any official art for it out of the Von Trapp pool.

As a side note, the first chapter gave us a name for the third eye girl! It's レシエ, though I'm not sure how it should be romanized. We also have ガルディアーク as the demon king's name.