Yes it will unlock the Osaka campaign achievement. The Road Map creator, Laus Domini doesnt mention it formally as the Osaka campaign but that is what he is eluding to in Step 6. The achievement guide said to play as Tokugawa but I found I just followed the road map and played as Toyotomi and constantly formed alliances with Tokugawa, keeping my 2 fiefs, and letting Tokugawa take over the rest of the Japan until it was just me and him left and then it finally triggered. I didnt follow the exact conditions he stated like the army size but it still triggered for me.
The Road Map states:
Winning "Incident at Honnoji" unlocks the "Battle of Sekigahara". Choose anyone for that scenario, wait a turn, and get the achievement. Now restart "Battle of Sekigahara". Remove Yukimura Sanada from the Sanada clan and place him in the Toyotomi Clan. Now play as Toyotomi, keeping just the two fiefs, defending when necessary. Make alliances with Tokugawa until 1614, making sure he survives. In the year 1614, make sure Toyotomi has only two fiefs, every officer is at or above 2000 troops, and Tokugawa officers have 5000+ troops. In 1615 the battle should trigger. It took me several reloads of a 1612 save for the battle to trigger, as there is no way of knowing if all Tokugawa officers have above 5000 troops. I was invaded by Tokugawa in the Fall of 1615, captured the officer, and the cutscene fortunately triggered afterwards. Achievement progress: 17/17
The achievement guide states:
First start a game on the "Battle of Sekigahara" scenario. Put Yukimura Sanada in the Toyotomi clan. Choose to play as Ieyasu Tokugawa. Now keep the toyotomi clan alive, an effective way to do this is ally with them and then help them defend their territory any time they are attacked. By 1615 you need to have conquered all the territories except the 2 owned by toyotomi. The battle will trigger between 1615 and 1619. A prompt will ask you if you want to participate. Accept, you don't need to win in order to get the achievement.
Last edited by n8ryder; 07-12-2009 at 08:31 AM.