Arima

The Arima family is a branch family of the Tohno family. Before the events of Tsukihime, Shiki had to move in with them because of his poor health, despite being the eldest son of the Tohno family. But Shiki came back to the Tohno household eight years afterward. During those eight years, Shiki became freinds with his non-blood related cousin, Miyako Arima, who continues to "protect" him even when he returns to the Tohno household.