You have to earn the trust of the Ninja Clan by giving them the Map of Phantom Forest, which Jack Barricade will give you as a quest reward.
In turn, to start that quest, you need to have completed ReVersal and Subani's Legacy.
ReVersal requires talking to Elpam Gorlab, going to Omega Sector, hunting drops, going back to NLC, going to Ludibrium, hunting more drops, and going back to NLC.
Subani's Legacy is just collecting quest items from Electrophants and I.AM.ROBOT.
All of this only requires level 50, but to get to Jack Barricade is difficult in 2nd job.
In turn, to start that quest, you need to have completed ReVersal and Subani's Legacy.
ReVersal requires talking to Elpam Gorlab, going to Omega Sector, hunting drops, going back to NLC, going to Ludibrium, hunting more drops, and going back to NLC.
Subani's Legacy is just collecting quest items from Electrophants and I.AM.ROBOT.
All of this only requires level 50, but to get to Jack Barricade is difficult in 2nd job.