Passage of Time
Pass Through, Manage
Tying a thread to a tombstone each year will help you manage the passage of time. That way you’ll know how many years you pass through, since you’ll have one thread for each year to count.
Dealing with the passage of time can be tough, so after you tie the thread to the tombstone, each year you eat a piece of cake (けい). You already eat cake to mark the passage of time on your birthday, so why not here as well?