"Five sacred Orbs were created to protect humans from the demons." -Takajo
The Five Orbs are introduced in Onimusha 2: Samurai's Destiny. Charity, Faith, Honesty, Respect and Strength.
Charity Orb is obtained from Takajo Takajo in Yagyu Village. It is used to open a wall that unlocks the boss fight with Ginghamphatts later on in Imasho.
Faith Orb is obtained from Oyu in a cutscene where Jubei asks her to lend it to him. It is placed in an iron Oni horse that takes them over Gifu Castle and back to Imasho.
Honesty Orb is obtained after slaying Jujudormah. It is then used later - on an Oni water vessel that takes Jubei to the Oni Sacred Place.
Respect Orb is obtained after the boss fight with Gogandantess . It is used to activate the Oni Genbu (an oni flying ship) that is stolen by Hideyoshi Tokichiro.
Strength Orb is obtained after defeating Ginghamphatts. It is used to open an elevator that takes Jubei to Nobunaga Oda.
In the final boss fight against the Golden Evil Statue, Jubei uses the Orbs to transform into a True Onimusha. His left arm becomes a cannon, his skin turns orange, blue markings appear on him, he grows horns and his eyes turn god-like.