Shell the green peas and cut the potatoes into bite-sized pieces. Soak the potatoes in water and drain.

Place peeled shrimp in a microwave-safe container, add sake and enough water to cover. Cover loosely with plastic wrap and microwave at 600W for 1.5 minutes. Drain and chop coarsely.

Place potatoes and green peas in a microwave-safe container, cover loosely with plastic wrap, and microwave at 600W for 5 minutes. Drain and mash coarsely with a fork. Let cool.

Combine mashed vegetables, shrimp, and seasonings (salt, black pepper, sesame oil) in a bowl. Divide the mixture into 6 portions.

Place one portion of filling onto each spring roll wrapper. Roll tightly and seal the edges with a mixture of flour and water. Repeat for all wrappers.