Cook the sushi rice until tender and fluffy. While it’s still warm, gently mix in the sushi seasoning so the rice absorbs the flavor evenly without becoming mushy.
In a mixing bowl, combine shredded imitation crab, Japanese mayo, ponzu sauce, cream cheese, and masago. Stir until everything is well blended and smooth.
In another bowl, mix the drained tuna with Japanese mayo, Korean chili paste, cream cheese, and black pepper. Stir gently so the tuna stays chunky but well coated.
Spread the seasoned rice evenly in the baking dish. Layer the creamy crab mixture on one side and the spicy tuna mixture on the other, or spread them evenly across the top.
Drizzle extra Japanese mayo and sprinkle furikake over the top. Broil for a few minutes until warmed through and lightly golden on top.