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).
Here is what I do know. When swallowing a liquid, it takes approximately one second to transit the mouth and pharynx and approximately one second in the esophagus (1). After that a small amount of water is absorbed in the stomach, and the majority is absorbed in the small intestine. am not certain I can give a direct answer as to the time it takes to get from the mouth to the bladder, because the route is not a direct one. However, drinking a large volume of water will result in increased frequency and volume of urination, although I don't have the data on how quickly that happens.