In a dish large enough to hold the steak, whisk together the shoyu, lime juice, oil, worcestershire, sugar, cumin, chili powder, and garlic until well combined. Poke a few holes with a fork on one side of the steak. This will help penetrate the steak with the marinade. Toss the steak in the marinade, turning to coat. Cover and refrigerate for 4 hours or up to overnight.
Preheat a grill to medium-high heat.
Grill the steak for 5 to 6 minutes on each side for medium-rare. See notes for a temperature guide. Transfer the steak to a cutting board, cover with foil and allow to rest for 5 minutes before slicing the steak against the grain.
Place the corn on the grill and cook until the kernels begin to char, rotating occasionally. You may hear the corn pop a bit. Transfer corn to a cutting board and set aside.
Lightly coat the onion slices with oil. Grill the onions on both sides to get some char marks, about 2 to 3 minutes on each side. Transfer onion to cutting board.
Cut the corn off the cob and place in a medium bowl. Chop the onion and add to the corn. Stir in the tomatoes, cilantro and basil. Add the garlic, lime zest, lime juice, maple syrup, oil, salt and pepper and mix well. Taste for seasoning. Serve corn salsa over steak or assemble corn on a platter and serve steak over it.