There are 12 Secret Missions, meaning you'll get 3 little bars with them only. Some of the blue orbs are scattered all over the missions. One blue orbs is obtained when you defeat all bosses in the Lost Souls Nirvana (Mission 18). Combat Adjudicators need to be destroyed, and added that, all the purchasable blue orbs via the Divinity Statues.
If you do all these, you'll get the twin full bars (20 little bars in total. 10 each bar.)^_^