[1] At a shinnenkai however, some of the Shogatsu festivities can carry over to the New Year’s party like the making of mochitsuki by pounding sweet steamed rice or kagamiwari which is the breaking open of sake barrels with a wooden hammer and drinking together.
Later on in the 18th century a new word was appearing in writings and was since then was known as a bōnenkai or year-end party and a shinnenkai is the same type of celebration.
[4] Although the Japanese have always been a people of great feeling and emotion as in the expression mono no aware, they are more reserved in expressing their feelings to others, so the shinnenkai has been a way of showing public displays of gratitude.
This is especially true for the company or business office shinnenkai where they can do bureikō or let their hair down and not worry about the boss/employee formal relationship or the rank and age divisions and have a good time.
[5] Some companies pay the entire cost of the party and will at times opt to not have the party at a traditional izakaya (restaurant and drinking places where the majority of shinnenkai are held) and instead have it on the business premises and save a lot of money in the process.