Works on any game mode.
For me, I just used Baek's "10 hit combo 2" (command list no.83 of 102)
Done in the practice mode because there is no time limit and used the Heavenly Garden stage because don't have walls.
Took me five minutes.
When you done the 10 hit combo without missing, before the last hit done a red globe with a "!" mark will appear.
Do 3 times on total and that's it.