5 hours max. All the challenges just take very little time. And the Fever Robo building will be finished by the time you finished the challenges. Do note that as long as you've done the challenge on one song, you can discontinue play and get another challenge.
For ee'mall songs and the like just go to special and play the minigames to get the points, each run should net you 10000 points. Enough for around 5 songs. There's about 20+? in the ee'mall category.
As long as you're focused with unlocking it should only take you around 3-4 hours at most.
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Originally Posted by Yuki I don't hear you~  | |