But, before watching the OVA and Specials, it’s recommended to complete the canon episodes.
I did not include the OVA and Specials in this list since those are not canon and more like a gag side-story! If you’re really into the series, then you’re free to watch those too.
Highschool DxD series has four seasons released at a span of six years. These are the best ways to watch High School DxD uncensored. High School DxD Hero (2018) Rating: R+ - Mild Nudity. High School DxD Born: Yomigaeranai Fushichou.High School DxD New: Oppai, Tsutsumimasu! High School DxD - High School DxD Hero (2018) Original Title: D×D.High School DxD Hero: Taiikukan-ura no Holy Special.
High School DxD Born: Ishibumi Ichiei Kanzen Kanshuu! Mousou Bakuyou Kaijo Original Video.