
Quick answer — Ichiei Ishibumi worked on High School DxD BorN (Original Creator), High School DxD NEW (Original Creator), High School DxD (Original Creator) and 3 more anime.
Ichiei Ishibumi worked on High School DxD BorN (Original Creator), High School DxD NEW (Original Creator), High School DxD (Original Creator), High School DxD HERO (Original Story), High School DxD: Fantasy Jiggles Unleashed (Original Creator), High School DxD OVA (Original Creator).