Origin
Mariko grew up with Miyamoto Usagi in his home village, along with her future husband Kenichi. As a member of the Samurai caste, Mariko must abide by Bushido as strictly as any warrior. For this reason, although she still loves Usagi, she cannot contemplate leaving her husband.
Creation
Mariko was created by Stan Sakai.
Character Development
As is eventually told throughout the saga, Usagi and Mariko had a brief affair just before Usagi left to serve Lord Minune. This resulted in Mariko getting pregnant. Kenichi married her shortly after despite Mariko telling him the father is Usagi, his hated rival. Usagi was not initially informed. Their son, Jotaro, was raised by Mariko and Kenichi and also was not told the truth about his parentage. The secret, and the relationship between these four characters, develops over the course of the Usagi saga. Currently both Jotaro and Usagi know the truth, but are not aware of the other’s knowledge.