Tosu (lavatory) (東司)
Tosu is a lavatory in Buddhist temples. In Temples of Zen sect, tosu is one of the important Buddhist temples.
Originally, 'tosu' meant a guardian god of the lavatory and called 'tojo' along with 'seijo.'
It seems that in ancient times, 'seijo' (west lavatory) and 'tojo' (east lavatory) were separately used according to the posts in the temple, but later, it was called 'tosu.'
There are few ancient structural remnants remaining as 'tosu.'