- Titles: Iki no kami, Sagami no kami
- Other name: Kasai Harukiyo
- Sons: Kasai Yoshishige, Kasai Kiyotaka
- Distinction: Warlord of Mutsu
Harunobu was a younger son of Kasai Harutane and a grandson of Date Tanemune. He held Teraike castle in the Toyoma district of Mutsu province. Harunobu inherited a family that was troubled by disputes both internal and external. He was at odds with the neighboring Ôsaki family, and in 1588 suffered the rebellion of one of his chief retainer families, the Hamada clan. By this time the Kasai clan were more or less subject to the whims of the Date, which had grown quite powerful under Masamune and had provided two of the last four Kasai lords (including Harunobu's father). In 1590 Harunobu was tardy in responding to Hideyoshi's summons to join the Siege of Odawara Castle in Sagami province and was deprived of his lands. While he went off into exile, former Kasai retainers rebelled and were crushed the following year.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005