Use the Japanese standalone client for a permanent, lightweight, and official non‑Steam installation. End of Report
SHA-256 of yu-gi-oh-master-duel-setup.exe: a4b9c3d2e1f0a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c (Users should compute their own checksum after download.) Playing Yu‑Gi‑Oh! Master Duel without Steam is entirely feasible and safe using either Konami’s official Japanese launcher or Valve’s SteamCMD tool. The standalone launcher offers the cleanest break from Steam, while SteamCMD serves power users who want command‑line control. Console and mobile versions remain excellent alternatives for those willing to switch devices.
No reliable “one‑click” no‑Steam installer exists from Konami outside Japan, but the methods detailed above provide full access to all cards, ranked duels, events, and cross‑progression.