Octopus sasakii is a species of octopus found only in salt water. This species is a taxon inquirendum.
It is able to change its color. It moves forward by vigorously squeezing water in its cloak and pumping it through the siphon.
It is carnivorous with a diet consisting mainly of fish, crabs, lobsters and molluscs, which it catches with the suction cups on its tentacles.
It is parasitized by Dicyema shimantoense, which infects its renal appendages.
The specific name honors the Japanese zoologist Madoka Sasaki who died in 1927.