Tsuruko is Motoko's elder sister and the current custodian of their family's Shinmeiryuu tradition. She no longer actively runs the school, having chosen marriage over a life dedicated to the sword. Her responsibility is to eventually transfer the school's leadership to Motoko when the time is right.
Despite Motoko's longstanding fear of Tsuruko, Tsuruko genuinely cares for her sister's well-being and only wishes for Motoko to find happiness in whatever path she chooses. However, Tsuruko has a tendency to react violently towards Motoko when she lies or omits crucial information. For instance, she tried to kill Motoko when she lied about being engaged to Keitaro to avoid returning to Kyoto, and also when Motoko failed to mention flunking the Todai entrance exam.
Similar to her sister, Tsuruko's sword techniques focus on eradicating evil through ki-infused slashes. These attacks can specifically target evil beings but are also powerful enough to cut through rocks, people, or larger objects.
In "Mahou Sensei Negima!", it was revealed that Tsuruko was the one who taught Setsuna and Tsukuyomi the Shinmei-ryu style of swordsmanship.
