Put cilantro and lime juice in a blender and purée until it becomes a bright green liquid. Add avocados and blend until the mixture reaches a mousse-like consistency. Chill until ready to serve.
Preheat the oven to 350°F. Line a baking sheet with parchment. Working in separate batches, scatter sesame seeds, morita chiles, nori, and bonito flakes on the baking sheet. Bake each until fragrant (keeping a close eye as they each cook at different rates) and chiles have puffed up.
In a food processor, crush chiles, nori, and bonito flakes separately. Combine with sesame seeds in a small bowl to make the furikake. Store in a sealed container.
Finely chop the tuna into small bits, similar to a traditional tartare.
In a small bowl, combine olive oil, soy sauce, salt to taste, and a squeeze of 2 lime wedges. Add the tuna and mix to combine. Chill until ready to serve.
To serve: Spread avocado purée on a tostada. Spread fish over the pureé. Sprinkle furikake over the fish, and garnish with wasabula greens and lime wedges.