Like January, February is a good time for visiting Japan as the weather is usually sunny and dry and sightseeing spots are not crowded. The downside of a visit in winter are the relatively short days (sunset is around 5:30pm in Tokyo) and the vegetation's barren state.
1 A healthy person drinking approximately 2 liters of water per day makes 800 to 2000 ml of urine per 24 hours (4).  If the urinary system is healthy, the bladder can hold up to 16 ounces (2 cups) of urine comfortably for 2 to 5 hours (5).
The materials that your body cannot use are sent to your large intestine, which finishes the digestion process by removing water, which takes 10 to 12 hours. It takes approximately 24 to 30 hours after the last food you took in to be completely processed, but it may take several days for it all to be eliminated.