Mitsubishi Temporary Headquarters (Building No. 22) (Taisho 7-1971) [Kotaro Sakurai and Taisho-era Architecture]

What did Sakurai's Mitsubishi Temporary Headquarters (hereinafter referred to as the Temporary Headquarters, south side of the current Mitsubishi Building) inherit and develop from the American-style office building that Yasuoka attempted with Building 21?
The plan is a courtyard with a U-shaped common corridor, and the main entrance is planned in the center, not on the intersection side, likely in consideration of access from Tokyo Station (1914), which has had an impact on the lifestyles of many people.
Next, looking at the plan, we can see that the number of rows of bricks or decorative bricks are shown. The concept of setting the floor heights of the Temporary Head Office (steel-framed brick construction) and Building 21 (SRC construction) inherits the concept of brick construction from the Meiji period.
Finally, we will introduce the elevation drawing from the Daimyo-koji side. Up until the 21st building, the red brick Queen Anne style had been inherited, but the temporary head office is Secession-style with white decorative brick. The box-shaped facade, including the tower design, is a departure from the Meiji era designs, and can be said to be an exterior design that feels like a new era.
By the way, why didn't they stick to the previous design?
Nobuyuki Ishihara recalls that he was ordered to redo the exterior, saying, "Make it a little more modern." Where are the blueprints for the Tudor-style exterior that Sakurai had completed?! We are currently searching for them.