Karigane is similar to Kukicha (Stem tea). Karigane is Kukicha made from the stem and twigs of Gyokuro or high grade Sencha. Karigane unlike other types of green tea, it's not made from tea leaves, but the stems and twigs.
Stems and twigs of green tea has its own special flavour and aroma which normal green tea doesn't have, and stems is rich in umami because this is the place where L-Theanine need to pass by before reaching to all tea leaves. Besides, Karigane contains lower caffeine therefore has low bitterness too.