The house locates in the high density's area in Tokyo. The exterior form with a staircase pattern was decided by the severe height limit by the building standards law. In this house, the client had many books.Planning the house, the rule was established at first. The rule was as follows: the structure of the house was painted in white, the supporting elements in black and the bookshelves in blue. The supporting elements were bay window, staircase, handrail, small eaves for rain and etc. Blue was chosen as the color that did not conform to the existence of books and erased the gravity of the books. While, white and black was coordinates of the color.In each space, the rule decided the finish of the interior automatically without strong relation with the space or function. So, the accidental combination of the three colors and the unexpected space appeared. It contributes to block the banalization generated by the invasion of many life things. In a usual house, the bookshelves are put in closed stack room or on the wall surrounding the room. In this house, the bookshelf space is used as passages for connecting the other spaces. The folding doors divide spaces. If opened, all rooms and bookshelf spaces are joined as one continuous space. When closed, the bookshelf spaces become buffer zone and each room gets independence.The bookshelf space also is a vertical passage for the natural light and wind. Through the FRP grating floor, the natural light from the top light window arrives until the lower floor. On the contrary, the wind elevates from the first floor to the high side window of second floor for exhausting the heat and the humidity.