To get Chaz follow these instructions: First when you get back on Grans Island (about to face Zeon) go to Yeel and play the piano in one of the houses. Then go to the church. The priest will think you're devils. Chaz will come and tell the priest otherwise. Follow them downstairs and they will talk about Zeon and the Holy sword when they stop talking Chaz will block your way, talk to him and he'll join you.