Valkyrie Hazard

A normal high school life is all Yuuto Suoh knows — until he gets yanked out of it and dropped into a parallel world built on Norse mythology. Now he's the head of the Wolf Clan — no training, no manual, just his modern-day instincts and a world full of people who operate by completely different rules. The setup leans into the culture clash between his contemporary mindset and the ancient, mythologically-rooted society around him, with various female characters who each carry their own abilities and agendas entering the picture as he tries to figure out his footing. As a one-episode OVA from 2019, it doesn't have the space to build something sprawling, so it keeps the focus tight on that initial collision between Yuuto's world and this new one. The Norse mythology angle gives it a bit more texture than the average isekai-adjacent adult title — think Valkyrie Drive: Mermaid or High School DxD in terms of the fantasy-meets-fanservice blend, though with a distinctly mythological flavor layered on top. If you liked Senran Kagura's approach of wrapping adult content inside a reasonably fleshed-out fictional world, this scratches a similar itch. It's a short watch, it knows exactly what it is, and the mythology hook at least gives the setting some personality beyond the baseline.