Step 1

In a large bowl, whisk together the five-spice powder, ginger, sake, rice vinegar, tamari, and sesame oil. Add the tuna steaks and turn to coat; allow to marinate for 30 minutes.

Step 2

Combine the crushed wasabi peas and brown sugar. Remove the tuna steaks from the marinade, and press into the pea mixture to coat. Pour the marinade into a small saucepan and bring to a simmer over medium-high heat. Reduce heat to medium, and simmer until the sauce has reduced and thickened, 5 to 10 minutes.

Step 3

While the sauce is cooking, sear the tuna in a small amount of oil in a skillet over medium-high heat to desired doneness. Pour sauce over tuna to serve.