There's a total of 20 Blue Orbs that are hidden and can be found or obtained from combat ads. There are also a total of 12 from secret missions giving a total of 32 fragments in total. Keep in mind that some fragments can be obtained with either Dante or Nero.
--Secret Mission Locations---
1- Terrace/Business District 2- Dining Room 3- Soldier's Graveyard 4- Angel Creation 5- Lapis River 6- Security Corridor 7- Meeting Room 8- Forest Entrance 9- Library (Bottom of Stairwell) 10- Master's Chamber (above the stave, behind mirror) 11- Fortuna Castle Gate 12- Opera House Plaza
--Secret Mission Notes--
- Secret Mission3
You need to beat Credo in mission 8 in order to obtain the grab and hold technique.
- Secret Mission 4
Red orb locations are randomized, pay attention to Nero's arm
- Secret Mission 7
Can also be finished with Dante using Pandora
- Secret Mission 8
Kill off 1 of the enemies. Finger poke attack timing is weird so avoid it. Block the other attacks instead.
- Secret Mission 9
This mission requires your own skill to finish. Shotgun is crucial in this fight. Go with Trickster and spam shotgun to keep the enemy at a distance while knocking them down. Also note that you can spam shotgun shots faster while falling after a jump.