The original game "Peke" was introduced in the original Chi No Rondo as a bonus game if you used the wrong System Card.This is the third original game that can be unlocked.
First, you need to select NORMAL BOSS RUSH mode.
Beat it two times, you will receive two Sound Discs.
The third time fight until you defeat Shaft and defeat the next boss, at the end of the fight you should be rewarded with original game "Peke".
Access it from the main screen like the other original games.
I advice to use Maria and her Dragon sub-weapon to fastly defeat the bosses.