- Birth: 1583
- Death: 1566
- Distinction: Lord of Shimabara
- Other name: Arima Sadazumi
- Sons: Arima Yoshisada and Ômura Sumitada
Haruzumi was first known as Arima Sadazumi and was locally powerful in Hizen's Shimabara region. He received the use of 'Haru' in his name from shôgun Ashikaga Yoshiharu, afterwards being called Haruzumi. Yoshiharu also gave him an honorific place in the shôbanshû, a private guard for the shôgun. He clashed with many local daimyô (including the Gotô, Hirai, Matsuura, Ômura, Saigô, and Taku) as he expanded the Arima to control five districts of Hizen Province.