Blue Tarps for Reservation (ブルーシート - Burū Shīto)
The iconic blue plastic tarps ('Blue Sheets') laid on the grass to reserve picnic spots. In Japan, placing a blue sheet serves as a universally respected marker of temporary seating ownership on a first-come, first-served basis.
Derived from highly durable, cheap waterproof industrial construction tarps introduced in the late 20th century. Their moisture blocking properties made them the default uniform of Japanese outdoor picnicking.
Find an open grassy spot early in the morning and secure your blue sheet using stones. Write your group name on the sheet. Ensure at least one member stays behind to guard the spot to avoid city cleanups.
What is the correct etiquette regarding 'Blue Sheet' picnic spot reservations in Japan?