Finely chop the smoked salmon into small pieces.

Combine the chopped smoked salmon with 2 tbsp Kewpie mayo in a mixing bowl.

Stir 2 tbsp sriracha into the salmon mixture until evenly coated.

Dice the cucumber and avocado into small bite-sized pieces.

Spread one piece of plastic wrap flat on the work surface.

Place about 1/2 cup cooked sushi rice in the center of the plastic wrap and press it into a flat round layer.

Place one-quarter of the spicy salmon mixture in the center of the rice.

Add one-quarter of the cucumber, avocado, and furikake seasoning over the salmon filling.

Lift the plastic-wrap edges around the filling and gather them together to enclose the rice.

Twist the top of the plastic wrap and gently shape the rice into a compact ball.

Combine sesame seeds with the remaining furikake seasoning on a shallow plate.

Unwrap the sushi ball and roll it in the sesame-furikake mixture until coated.

Repeat the shaping and coating process to make three more sushi balls.

Drizzle the sushi balls with additional Kewpie mayo and sriracha, if desired.

Top with sliced jalapeño, if desired, and serve with soy sauce for dipping.