The company behind the customizable Traveler’s Notebook/Midori Diary makes a lot of other fun stationery products, like its series of secret sticky notes:
“Each Post-it style note is designed to be folded up so that your written message is hidden and secret. When folded, the bottom half sits securely under the top half, showcasing the cute design. When unfolded, the image and note is revealed in all its glory.”
There are a wide variety of these, but my favorite is this kissing couple, perfect for marking romantic moments or passing sweet notes to your partner. The one with the dude’s wild haircut is also great lol:
Each pack includes 20 notes. A lot of import stationery shops are carrying these, including this Etsy one, which has the packs for around $6 each before shipping.