• shikoku,
• ahikoku,
• zhikoku,
• xhikoku,
• dhikoku,
• ehikoku,
• whikoku,
• sgikoku,
• shikomu,
• shikokku,
• shicoku,
• sjizoku,
• Shizouko,
• Schizoku,
• shickoku,
• shikoko,
• schikoku,
• shikukou,
• shicokou,
• schickoku

• Shizuko.

The adjective form of the word "Shikoku" is "Shikokuan".

The plural form of the word "shikoku" remains the same, as it is already a plural noun. "Shikoku" is the name of one of the main islands of Japan and does not change in form when referring to multiple islands.

The singular form of the word "shikoku" is "shikoku". The word is already in its singular form as it is a proper noun representing one of the four main islands of Japan.