>>1825925This one.
http://www.toranoana.jp/mailorder/cot/pagekit/0000/00/04/000000046852/index.htmlI have the compilation as you saw before, but the images for this volume weren't in it. As far as I know, the compilation contains volumes 1-5 of the series and it doesn't count as a volume itself. This Vol. 6 was released last year apparently. I can't believe I haven't seen it until now.
Metroidvania, huh? Sounds like it'd work well frankly. The capability to keep it rather Disgaea like would be astronomical were it to use a similar system.