Prepare the sushi rice according to package instructions, about 20 minutes. Let it cool slightly.

In a skillet, heat olive oil over medium-high heat. Toss peeled shrimp with garlic powder, onion powder, paprika, chili powder, oregano, and salt. Cook shrimp for 2 minutes per side until opaque and golden. Transfer to a plate to cool.

Mash ripe avocados with a fork until creamy but slightly chunky. Add lime juice and a pinch of salt. Set aside.

Combine Kewpie mayo with Sriracha in a small bowl until smooth. Set aside to blend flavors.

Slice cucumbers in half lengthwise and scoop out seeds to create boat shapes.

Assemble the boats by layering sushi rice, cooked shrimp, and mashed avocado. Drizzle spicy mayo on top.