Musubi (His alpha of his harem. I mean, c'mon, she's adorable and can punch people hard.)

Rias, Akeno, Koneko, Xenovia (Ignore kiba, Gasper, and Asia. Remember folks, Issei will have Asia in this story)

Sona and her peerage.

Karasuba

Venelana and Grayfia

Raynare

Mittelt

Kuroka

Serafall leviathan

Kalawarner

Irina Shidou

Taki

Yasaka

Rossweisse

Matsu

Kazehana

Viser

Akitsu

Mio (Rias's cousin)

(That's it for his harem, and he'll have Riser's peerage and his sister after Y/n have beaten him.)