I think you may be referring to "High School DxD", which is a popular Japanese light novel series that has also been adapted into anime. However, I'm not sure about the "3" at the end.

The main High School DxD series includes:

1. High School DxD (first season anime)

2. High School DxD New (second season)

3. High School DxD BorN (third season)

If you're asking about the third season, it's called "High School DxD BorN". It aired in 2015 and covers volumes 7-10 of the light novel series.

Is this what you were looking for? Or did you have a different question about the High School DxD series?