To resolve all the bad blood and conflict of the past between the Three Giants, Loki, Hirate and Boris once held a secret meeting in Kiyosu Castle in Aichi prefecture of japan.
The Kiyosu Kaigi as the people of the Empire of Japan called it. Hirate undoubtedly was trying to repeat the famous Kiyosu Kaigi.
The Kiyosu Kaigi in history is about the meeting in Kiyosu after the death of Oda Nobunaga to decide the matter of who shall succeed Oda Nobunaga.
Only this new meeting inside Kiyosu Castle did not determine the succession of a family clan, instead it talked about the matters of the past and the plans for the future
This small meeting, attended only by the few, created a period of tense diplomatic situation with the other Four Great Powers trying to infiltrate the meeting.
The end result of the meeting was that it forged an alliance between the Three Original Great Powers.