Highschool DxD is one of those anime that really hooks you with its mix of action and, well, fan service. If you're looking to watch it online for free, there are a few places I’ve stumbled upon over the years. Sites like Crunchyroll sometimes offer free episodes with ads, though their catalog varies by region. Then there are unofficial streaming sites—names like 9anime or Gogoanime pop up a lot in forums. I’ve used them before, but be cautious; the ads can be aggressive, and the legality is murky.
Personally, I prefer supporting official releases when possible, but I get it—budgets are tight. If you go the unofficial route, a good ad blocker is a must. Also, keep an eye out for community recommendations; Reddit’s r/animepiracy has threads discussing the safest options. Just remember, free often comes with trade-offs, whether it’s video quality or pop-ups.