KanjiJLPT N1
Page

page, leaf

Mnemonic

One drop of ink falls onto your money, staining the bill completely. Rather than waste it, you flip it over and use the blank side as a page to scribble your grocery list. You press the one drop flat, and now every piece of money doubles as a page in your makeshift notebook.
Additional thoughts
Picture a crisp bill with a single ink drop spreading across it — the moment you flip it, it transforms into lined notebook paper. The physicality of flipping money into a page reinforces the kanji's structure: one + drop sitting atop money.
Quick recall
One drop of ink ruins your money, so you flip it over and use it as a page.

Details

The keyword for 頁 is page. This kanji originally depicted a human head, and in its earliest usage it referred to the head or face. Over time, it came to mean a page of a book, likely because pages are read by turning them one by one, much like counting heads. In modern Japanese, it is commonly used as the counter or unit for pages in books and documents.
On'yomi
けつ
Kun'yomi
ぺえじ、おおがい、かしら