As mentioned in previous postings; Japanese sake lubricates the wheels of social interaction. Around this time of year companies in Japan have after-hours drinking parties where co-workers binge on alcohol with their supervisors, or with friends. This type of gathering is sometimes referred to as " forget the year gathering." I personally no longer attend such gatherings unless nihonshu is on the menu. If I'm going to further damage my liver, then let me drink the good stuff, at least.
Some salarymen dread this awful get together, and would much rather be with real friends or with family than co-workers. One acquaintance of mine told me that one big reason he hates these get-togethers is because he has to perform something in Japanese called "goma-suri" ( sesame grinding), the literal meaning would be something like brown nosing or kissing ass in English whereby the junior salarymen would have to pour sake for the seniors and be little errand boys, sometimes until 3a.m., and then be expected to wake up at 5am for work a few hours later.
In my years of visiting onsen(s) around Japan I have witnessed and have even taken part in these types of drinking parties. If you are lodging at an onsen ryoukan(traditional Japanese hotel), then these parties are nice because you know you can just crash on the tatami and not worry about catching a train or waking up for work the next day.
Inhibitions at these parties are also lower. I love drinking with Japanese women at these get-togethers. Just be natural, let the sake flow, and let nature take its course.