You must get EPISODE COMPLETE! in every single area of Spira in CH5.
i.e
-About The Calm Land :
start PR mission, do pitching, or lose credits at minigames for points;
if one of the companies gained 400+ points already, Calm Lands will become HOTSPOT, so simply visit the area for final scenes, in which Tobli is made manager of both companies
if you were unsuccessful in gaining enough points to bring one company to lv5 before CH5, all is not lost; you can play minigames for the company you're advertising for until you get 400+ points; now go to Celsius and talk to Buddy - Calm lands will become a HOTSPOT and voila.
-About Guadosalam Area :
in CH3 make sure you complete the mission on Gagazet where you must defeat Garik in boss battle, So the Guados return to Guadosalam
with Tromell as their leader in CH5.
-About Zanarkand :
Do not leave Zanarkand HOTSPOT for last, clear it out first ASAP!
-About Mi'ihen Highroad Area :
in CH5 Chocobo Eater is not the only culprit you can go after if you're
attempting to get mascot. Nabbing Rikku or Calli will ensure EPCOM for
Mi'ihen as well. But be careful! If you end up with Rin or Prophet to be
the responsible party, this causes you to get EPISODE COMPLETE for Mi'ihen, thus screwing you out of mascot.
Anywho...
completing Via Infinito, finding Ruin Depths or Fiend Colony dungeon, as well as bridal mission ISN'T required to get this DSP.