Sojiro Nishikado (西門 総二郎,Nishikado Sōjirō) was a part of the sixteenth generation of the Nishikado family and the current head of the family's tea school. He was a member of the F4 and attended Eitoku Academy.
Sojiro entered Eitoku Senior High, after graduating from the school's middle school. Him and his friends, the F4 controlled the school and were feared by the students and staff. Partly to amuse themselves, they began giving out "declarations of war" (a red card) to those who defied them, including Kimoto.
The F4 first met Tsukushi, when her friend Makiko Endo landed on Tsukasa Domyoji after falling down the stairs. Tsukushi protected her friend, earning herself a red card. However, she decided to fight back and declared war on the F4, which Sojiro and Akira found "spunky".
After graduating high school, Sojiro began to attend Eitoku University with Akira and Rui. During his second year, he attended Shizuka's wedding in France. While continuing his education, Sojiro became the Grand Master of his family's tea house.