Shizuru Kuwabara is the older sister of Kazuma Kuwabara.
Tough-as-nails, somewhat deadpan and with a stronger sixth sense than Kazuma, Shizuru is very similar to Atsuko Urameshi, in that she wants her little brother to make something of himself, instead of fighting on the street. She made her first appearance briefly before Yusuke and Kuwabara first went to rescue Yukina from Tarukane.
Shizuru is also present in the audience alongside Keiko and Botan, at the Dark Tournament. She develops a romantic interest in Sakyo, who had saved her life twice during the saga. His death at the end of the tournament was what ultimately cut that romance short.
After the Chapter Black Saga, Shizuru finally pressures Kuwabara to pursue his studies.