One-to-one ceremony

...It may also refer to the gifts given at such occasions. There are various forms of New Year's celebrations, such as a formal visit and banquet, a Kadorei ceremony where prayers are exchanged at the gate or entrance and people make their rounds, and abbreviated New Year's celebrations called General Rei, Ittourei, or a business card exchange where people from the area gather together. Originally, it was a ceremony where members of the family would stay at the main house and spend the New Year's night together to worship and welcome their ancestors and the New Year's gods. In Shikoku and other areas, there is a custom called Kado-aki, where all members of the branch family go to open the front door of the main house early in the morning on New Year's Day. These family events expanded to include local ties and other areas, and developed into village New Year's customs where all households are visited, and in cities, New Year's celebrations where merchants visit their customers and superiors at work, and even the development of New Year's cards that do not involve any visits at all.

*Some of the terminology explanations that refer to "Ittouri" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…またその際の贈答の品をいう場合もある。年始の形式には正式に訪問して饗宴を受けるもの，門礼（かどれい）といい門口や玄関で祝詞を交わすのみで次々と回礼して歩くもの，また総礼，一統礼（いつとうれい），名刺交換会などと称し，回礼を省略化し地域の者が一堂に会して行うものなどさまざまあるが，本来は一族の者が本家に参籠し，歳夜をともに明かして祖霊や歳神を祭り迎える儀式であったといわれている。四国などには，元日の朝早く分家一同が本家の表戸を開けに行く門開きと呼ばれる習俗も残されており，こうした一族の行事が地縁その他に拡張され，村年始といった全戸を回礼する習俗や，また都市にいたっては商家の顧客回りや職場の上司への年始，さらには訪問をいっさい欠いた年賀状の発達などに進展していったものと思われる。…

※「一統礼」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報