When the Map builder tool for Aggressors came out, I made several maps. While playing with this new toy, I decided to make a new scenario with these maps. Eventually I selected two scenario candidates: one was a scenario about the Sengoku period of Japan, the other about medieval Europe, but I decided to make the former because as a native Japanese, I could more easily gather necessary materials such as flags and faction pictures for the diplomacy screen; also I wanted to make a scenario about completely new circumstances and factions.
Europe was already represented in the Mediterranean main scenario and several user-created scenarios. Finally I thought the Sengoku period was more suitable for the game engine, because eventually during the Sengoku period, Japan was united by Oda/Toyotomi clan like Roman Republic did with the Mediterranean coasts. On the other hand, medieval Europe was never united by one powerful faction; consequently that scenario must be an alternative history one (to be honest I don't much care about historical persuasiveness though). For these reasons, I decided to make the Sengoku one.
One of the challenges I've meet in developing the scenario/mod was gathering suitable pictures for event graphics. I chose these pictures from Ukiyoe, traditional Japanese art and several pictures of Sengoku period, but too many event graphics were required. Also testing game balance was a never-ending task. I myself am not a good strategy gamer; I usually play the game at the Noob difficulty. But the Sengoku scenario was even more difficult than the Mediterranean main scenario, so testing the scenario was (and is) very challenging.
Seems like users have enjoyed my scenario/map, and send a lot of opinions, which helps further development of the scenario/mod. Also I want to make more Objectives. But all in all I've been satisfied with the current version of the scenario/mod. Perhaps I'll make a Medieval Europa version and other periods of history too. I realized while making the Sengoku scenario that this engine, especially the AIs, are excellent for these scenarios.