Okay, the user wants me to translate "increased rapidly" into Japanese. Let me think about the correct translation.
First, "increased" is 増加した or 増えた. "Rapidly" can be 快速に or 急速に. So combining them, maybe "急速に増加した" or "快速に増加した".
But I should check which is more natural. "急速に" is commonly used for rapid increase. "快速に" might be more about speed, like in transportation. So "急速に増加した" sounds better here.
Also, the user mentioned if the content is already in Japanese, leave it as is. But the input here is in English, so translation is needed. The rules say to provide only the translation, no explanations. So the answer should be just the Japanese phrase without any extra text.