した, さ, くだ, お
There's a toe below ground.
You keep digging for the toe below the ground, and instead of hitting a toe you hit something hard and metallic. You keep digging and digging around it, but it's huge. Turns out, you found yourself a car (か). Keep digging until you unearth the car. Inside, you find the toe you were looking for.
Currently there are no similar looking kanji which exist in the WaniKani learning system