The Kushanku from the Choto Kyan line is called "Chatan Yara no Kushanku." It is a bit different from the Itosu/Sakugawa lineage Kushanku, but in the same ball park. It is considered the highest kata of the Matsubayashi Shorin ryu. We consider Gojushiho to be one of the highest kata. Kosokun Dai is usually taught for shodan/nidan.