1)Koutetsu no Daitenshi 2)Datenshi ni Sasageru Uta 3)Doutei Saizensen 4)Datenshi dj - Harem Nights (a side story) 5)Bed no Shita no Himitsu 6)Datenshi Ni Sasageru Uta Dj - Family Visit (side story)
Oops i just read Harem Nights before Koutestse No Daitenshi. So Im started from the beginning. Does Rosenburg's younger brother Kurt feature in all this series? He should have his own story along with Hans or perhaps teaming up together for a smut filled adventure..
The series in order
1)Koutetsu no Daitenshi
2)Datenshi ni Sasageru Uta
3)Doutei Saizensen
4)Datenshi dj - Harem Nights (a side story)
5)Bed no Shita no Himitsu
6)Datenshi Ni Sasageru Uta Dj - Family Visit (side story)
Hope this will help:)