I just saw High school DxD and I'm going through a crossover binge with Naruto. Here are a few fics I've read that I find pretty good. Irregular Metronome - Naruto and Sasuke wake up in a new universe where Naruto is now nobility and Sasuke is a street rat. The story is a bout them making their way to the top in terms of strength. It's sufficiently long and well written. As with all DxD crossovers it looks like it could end up being a multi pairing. Devil Ninja- Naruto ends up in the Dxd universe and it basically follows the Dxd story line with Naruto as the MC. II recommend this fic since "Engulfing Silence" is a pretty decent author although sometimes it's hard to want to stick with his fics. A Simple Teenage Shop Owner- I really liked this one best of all. Naruto opens a sweet shop in his new world. Only he keeps getting propositioned by all the different factions to join them and they love his cooking. Naruto is pretty much the strongest character in this fic, but the author somehow has been able to make every battle interesting.