This is an excellent translation of Kaori Ekuni's 1991 novel, "Kira Kira Hikaru," a popular best seller that was made into a very good film by Joji Matsuoka the following year.
It is, like most comedies of manners, about a marriage -- though of a rather different kind. Neither bride nor groom is marriageable material. He has a boyfriend to whom he is faithful, and she is an alcoholic, faithful mainly to her bottle.
When the two discover, during their "arranged" meeting, their mutual lack of qualifications, they both decide that this is an excellent reason for marriage because it at least gets their parents off their backs.