Grilling a thick Wagyu steak requires Reverse Searing: starting with about 30 minutes to 1 hour of low heat, depending on the thickness of the steak, bringing the internal temperature of the steak up to personal preference, rare (45°C/ 113°F), medium rare (50°C/ 122°F). After that the steak is grilled over high heat for 1 to 2 minutes each side to build up a flavourful crust. Taking the steak off low heat and applying direct high heat for some minutes will add roughly 5°C to the internal temperature of the steak.

Sirloin Steak (Striploin Steak), from grass-fed, free roaming (lean) Wagyu in New Zealand. Wagyu in Japan is usually grain-fed and therefore more marbled with fat.
Grass-Fed Wagyu is lower in marbling but higher in Omega-3 fatty acids, Vitamin E, Potassium, Iron and Zinc.