Sengoku Rance:Story

WARNING, SPOILERS AHEAD

The Beginning
Initially, Rance was just touring JAPAN with Sill for an onsen trip with the ultimate goal of H-ing JAPAN's famed beauty, Princesss Aroma. Along the way,Rance was mostly just H-ing people. One day they stopped by a tango house, and met Nobunaga and Princess Aroma (who turn out to be way under the age limit for Rance) of the Oda Clan. Nobunaga and Aroma enjoy the lives of ordinary folks, which is why they often disguise as commoners and work in the tango (several balls with a stick going through them) place. Incidentally, tangos made by Aroma are... inedible... Nobunaga and Rance got along very well. Eventually Nobunaga lets Rance run the Oda house from behind the scenes, because Nobunaga doesn't want to deal with the politics and all, finding it too much a bother.

The Possession of Nobunaga
The Demon Xavier was previously sealed in 8 different gourds. Each gourd was entrusted to 8 different houses by Tenshiism to be guarded through the future generations. Nobunaga's monkey broke the one kept by Oda house, so a portion of Xavier's essence escaped, and possessed Nobunaga. Using Nobonaga's influence, Xavier began organizing a secret group of ninjas directly under his command and began seeking out the gourds kept by the other houses. During this time, Xavier (in Nobunaga's body) publicly proclaimed to be ill, and moved to live in the Honnou Temple where his body may get more rest.