Obtained: When you receive a Topic from her, head on over to Fortuna Office and speak to her directly.
After the cutscene, make your way to Daitou TV Station and enter the Idolasphere to trigger a cutscene. Afterwards, teleport to Film Set B: Indoors (1F) and travel to the boss room. *NOTE: You will need to have Tsubasa in your party in order to cross the bridge. Once you enter the boss room, a cutscene will trigger. When prompted choose “I believe in Tsubasa!” then sit back and watch the cutscene. A boss fight with Pheros who is level 46 and two Level 44 Red Barbarians will ensue following the cutscene. Defeat them to trigger a cutscene. Afterwards, travel to Bloom Palace to unlock Tsubasa’s new Radiant Skill called “Door of the Skies”.