“ii” in Japanese is usually the adjective いい , and its negative form is よくない. If you meant the phrase 「〜がいい」 or 「〜でいい」 , the negative often changes depending on the exact sentence, but いい → よくない is the basic form.

Quick examples

  • いい → よくない
  • この店はいい。→ この店はよくない 。
  • 今日はいい。→ 今日はよくない 。

Small nuance

  • いい is the irregular form; it behaves like よい in some grammar explanations, which is why the negative becomes よくない rather than something like “ii nai.”
  • If you were asking about “I’m okay / no thanks” in conversation, people often use いい differently depending on context.

If you want, I can also show the negative form for 「〜がいい」 vs 「〜でいい」 with a few natural examples.