A formal Japanese letter follows a fixed frame. When it opens with a tōgo, an opening word such as haikei, it should, as a rule, close with a ketsugo, a closing word such as keigu. A Mynavi guide calls this the principle.
In a business letter, the opening word is followed by a seasonal greeting and then the body. One sample greeting in the guide begins kunpū no kō, in the season of the fragrant breeze.