Ok so before the list I want to say a couple of things. I've done read a couple of Fan fic of highschool dxd where some of the girls decided to date other guys just because they wanted to understand Issie more so I will leave it at that. Now further ado here is the list
Highschool dxd
Akeno Himjima ( Main)
Kuroka
Xenovia Corta
Orphis
Elisha ( Fem. Ddrage)
Tiamat The Kaos Karma Dragon
Grayfia Lusifuge
Velelana Gremory
Yasaka
Penemue
,(A/N if you want to add anyone to the Dxd Harem let me know)