Ichinichi joshaken (one-day pass)
What a one-day pass is
A one-day pass is a ticket that lets you get on and off the routes it covers, with no limit on the number of rides, throughout one set day. The easiest way to think of it is that instead of paying a fare every time you board, you buy a whole day's worth of unlimited travel in one go. Toei Bus has a one-day pass valid on Toei buses, and passes of a type that also cover the Toei Subway, the Toden streetcar and more are on sale as well. How far each pass takes you differs from one kind to the next, so the first step is to pick the pass that suits the day you have planned.
The kinds of pass, their prices and the ways to buy them can change, so check the official site of the Tokyo Metropolitan Bureau of Transportation when you come to use one. On this site, our article on the Toei Bus one-day pass covers how to choose in detail.
Working out whether it pays for itself
Holding a one-day pass changes the very way you get around. Since you need not keep an eye on the fare for each ride, you are free to move in the spirit of "board first, get off wherever looks interesting." On a day of hopping between two or three places to shop, a day of errands that takes you from one counter to another, a walk around town on a day off: if you plan to ride the bus repeatedly within the same day, the pass is worth considering.
The rule of thumb for deciding is simple. Ask whether the number of times you will ride that day, multiplied by a single fare, comes to more than the price of the one-day pass. Toei buses charge a flat fare that does not vary with distance, which makes this sum an easy one to do. Even on a day when the number of rides is borderline, if you value the lightness of being able to hop off wherever you please, a small difference in price is well worth paying.
How it differs from the Silver Pass and IC cards
Let us sort out the difference from the things it is easily confused with. The Silver Pass is a travel pass limited to a particular group, Tokyo residents aged 70 and over, and it can be used right through its period of validity; the one-day pass, by contrast, is on sale to anyone and is valid for that one day alone. The division of roles runs like this: the Silver Pass for getting about day to day, the one-day pass for a ride-all-you-like day taken by someone who has no Silver Pass.
A transit IC card is a means of payment that deducts the fare from the remaining balance each time you ride; the card itself carries no unlimited-ride effect. One-day passes come in several forms as regards the style of the ticket and the way it is bought, and these can change, so it is reassuring to check the official site for the purchase method at the time you intend to use one.