Koiwa Morichika served as a bushō during the Sengoku period.  He was the lord of Koiwatake in the Azumi District of Shinano Province.

The Koiwa were kokujin, or provincial landowners, and a branch of the Nishina clan which, in turn, descended from Minamoto no Yorisue of the Seiwa-Genji.

In 1522, Morichika was appointed to serve as the lord of Koiwatake Castle.  When, during the Tenbun era (1532 to 1555), Takeda Harunobu (Shingen) invaded Shinano, Morichika and the entire Nishina clan including cadet families resisted but were defeated in all instances.  In 1551, he was attacked by the Takeda army and an outlying base known as Yado Castle was toppled.

In 1552, Morichika, along with a garrison of 500 men, was attacked by an army five times the size at Koiwa Castle.  On this occasion, Morichika and his youngest son, Koiwa Moriyasu, took their own lives.