In ancient Japan, including the time of Genji, There was no formal “marriage” or “wedding” when a man and woman got married.
It was this simple:
If a man was interested in a woman, he wrote to her that he was interested in seeing her. Back then, it was not common that men could physically “see” single women who were supposed to be hiding behind the curtains.
Besides, “seeing a woman” meant “getting married,” or “having sex.”
Thus, asking a woman that he wanted to “see” her, it was already a marriage proposal. What they did first was just exchanging letters with poems, waka, along with seasonal flowers or beautiful scented paper.
Once the woman accepted the man’s proposal, which usually took months or sometimes years, he visited the woman at night and “saw” her. There was no electricity and the lights were dim. So he would not see her very well. But they talked to each other and had sex anyway.
Talking to each other was an important aspect. They would discover whether or not they were writing the letter and poems themselves. Some people cheated and had someone else write to attract the other sex. If they did not like each other after they talked, or at least he did not like her, he did not visit her again.
He was supposed to leave before dawn. Right after he left, he would write a beautiful letter to her, saying it was such a fantastic night.
How soon he wrote indicated how much he liked her. Sooner the better, like returning business emails in these days.
While they were having their date in the woman’s room, her nanny and servants were usually waiting in the attached room. Yes, they knew what was going on in her room, including the man-woman stuff. After the man left, the nanny and servants reported to her parents who visited their daughter.
If the man visited her three consecutive nights, they were considered to be “married.” There was no paperwork or oath. On the third night, the woman’s parents prepared a banquet to welcome the man as their daughters “husband.” That was it.
“… Marriage was basically settled between the husband-to-be and his fiance’s father. Settlement of marriage was determined only by approval from the woman’s father, that is, the only key person was the father of the bride. Ancient wedding ceremonies were very private and simple. “Momotori no tsukue shiromono,” which can be regarded as an equivalent to present day wedding ceremonies, was only a banquet for the bridegroom provided by the bride’s father.”
(Excerpt from “Marriage and Divorce in Ancient Heian Japan“)