@Tcof I think the mangaka draws a new chapter each day, so it reflects time passing in the real world rather than in the manga (so literally after 100 days in the real world the two characters will be married). I had the same question and that's the only explanation that made sense to me.
@GavinFreud@Tcof@Soulwarfare There will be 100 chapters with 1 chapter a day in the real world. And in their world there will be 100 days between the first and last chapter. (But that doesn't mean that 1 chapter is 1 day in their world.)