As Karpeles had initially not been formally charged for a crime, authorities could not legally detain him for more than 23 days at a time.
so what arrested for few day then went out . ?
if u ask to spend few day in jail in exchange of million of dollars i am pretty sure that most people will happily go to jail

23 days applied to an earlier arrest before he was charged with a crime. Now he's been charged with embezzlement and remains in jail. Given Japan's conviction rates he's likely to spend quite a bit of time there.