He is the unnamed boss of Z. Z's Boss is a "miscalulated clone" of the ESP. As he is the son of one of the ESP's clones. This has also caused hatred and rebellion, which lead Z's Boss to create the Z organzation. Z's boss is an alice and he shares the same Alice as the ESP; the Clone Alice. He, like the ESP, wants Yuka to accomplish his goals.
When Yuka goes to the Z organzation Z's Boss expresses interest in her Alice abilites and wants to use her similar to what the ESP did. Yuka at first, refuses to corrperate with his organzation after learning that Z's Boss is related to the ESP by being a son of one his clones, but chooses to in order to stop the ESP.
High School Division Arc
During this arc, Z's Boss and his organization attack the school. He is likely trying to take it over. As they go on, students from Gakuen Alice are being abducted. The attacks stop due to Shiki making a deal with the ESP to stop the invasion.
In Chapter 145, Z's Boss is seen weak and coughing. It could possibly, be because of his connection to the ESP as the ESP is also shown weak and coughing. The ESP has plans to maniuplate him and gain control of the Z organzation by using the Clone Alice stones he forced Shiki to return. Z's boss willingly arrives at the academy and is greeted by the ESP, who calls him his other self. During the concert, Z' boss stands by the ESP after Reo fails to attack him and shoots Narumi to protect the ESP from him.
Z's Boss inherited the Clone Alice from the ESP. According to Shiki his Alice is significtly weaker then the ESP. Using Yuka's Stealing Alice and Insertion Alice Z's Boss has gained more power by having Clone Alice stones inserted into him. This has enabled him to resist the control of the ESP and have the ability to maniuplate the ESP's clones.