Install QCMA (wololo.net) Setup a video folder location for QCMA. (Usually in C:\Users\xxx\Videos) Put DISGAEA3_EU.vpk in the video folder. Rename DISGAEA3_EU.vpk to DISGAEA3_EU.mp4 (refresh qcma database)
Open CMA on vita and transfer/copy the game through video transfer. Open Vitashell/Henkaku (wololo.net) go to uxo:/video/xx/DISGAEA3_EU.mp4 Move DISGAEA3_EU.mp4 to uxo:/VPK Rename it back to DISGAEA3_EU.vpk Install, enjoy the game!
To save space, delete the game vpk from uxo:/VPK after install