We are in a point in history where many Japanese architects work with designs outside the country. Many domestic projects are inviting architects from outside Japan as well. It is believed that these practices will become even more common as time progresses. There are regional differences in the development of designing, and there are relevant regulations and customs as well. Such differences are seen in task divisions and drawings. Taking these into account, this research focused on design architects (DA), which is increasingly taken part in domestic projects as design supervisors in recent years. By examining the case where Nakanoshima Mitsui Building hired a U.S. architect company as DA, we clarified its role and how they conduct their tasks. Also, by studying and analyzing the Design Development (DD) drawing used in architectural projects, which is an U.S. style blueprint, characteristics of the DD drawings has been identified.<br><br> The results of this study are as followings.<br> ·It was found that the term DA has become common as the name for the position that supervises designs along with the practice of task division in advanced and complex large scale projects after the year 2000.<br><br> ·Since DA are not involved with costs of buildings, scheduling and applications, it can be said that it is “a position that is not subject to administrative punishment and can concentrate on designing.”<br><br> ·It was found that while DD drawing is part of the schematic design phase in the first half of the design process, it is also relevant to the design development phase in the latter half of the design process, and that it is a unique design process that adopted and applied the US style DD to Japan's design process.<br><br> The following characteristics were observed in the techniques used in DD drawings.<br> ·Partial drawing - By using many plans with floor plan, elevation, cross section and materials all in one drawing, it straightforwardly communicates the details of the space to be created.<br><br> ·Design Priority - By writing the designs' order of priority, The DD drawing does not only serve as a blueprint during the construction of the building but also as a design guideline. This enables the priorities to be shared during modifications.<br><br> ·3D modeling supplements the intuitive understanding of complex 3D structures and details, and its main purpose is to communicate the design accurately.<br><br> ·Unlike the structure of Japan's blueprints where drawings are grouped based on its type, it was found that the structure of DD drawings groups certain spaces and parts together.