Remove the plastic film wrapper of the kani and discard.
Press each kani from tip to tip between your fingers. Pull apart to shred.
Thinly slice carrot, and julienne (cut into matchsticks).
Do the same with the cucumber
Cut the mango; discard the stone.
Slash diagonally, the slashes about a quarter inch apart, all the way but without cutting through the skin.
Using a spoon, scoop out shallowly to come up with thin strips.
Rinse the lettuce and dry in a salad spinner. Cut the leaves horizontally into half-inch slices.
Place the shredded kani, julienned carrot and cucumber, sliced mango and lettuce in a mixing bowl.
Drizzle in the sesame seed oil.
Toss to distribute the ingredients evenly. Use your hands to toss to avoid bruising the ingredients.
Add the Japanese mayo. Toss the kani salad once more to moisten everything evenly.