Step 1: Location. The Senkaku Islands are a group of uninhabited islands in the East China Sea. Step 2: Dispute. Both China (calls them Diaoyu Islands) and Japan (calls them Senkaku Islands) claim sovereignty. Step 3: Strategic importance. These islands are located near important shipping lanes and are believed to contain oil and gas reserves. Step 4: Conclude. Thus, the dispute is between China and Japan.
\[
\boxed{\text{China and Japan}}
\]