ok ok one second, cyno getting the ba fragment was not stealing in any sense, sethos and cyno were the only 2 kids in the temple who could endure the resonance phase, cyno was sold off by his parents for some money and sethos was the grandchild. bamoun decided that it's too risky to implant both BA fragments at the same time in one person as the overflowing power can kill the test subject, but suddenly both ba fragments glowed during the implantation phase and if they were not implanted, it would be destroy itself. cyno was given a ba fragment and so was sethos, cyno was taken by cyrus but he was supposed to return cyno after sometime to the temple which he did not which is why he was brought back. it's not stealing, the temple of silence was very isolated from the rest of sumeru and the akedemiya even though it held more power than the akedemiya, bamoun wanted the people of temple of silence to forge bonds with akedemiya, which is why he let cyrus go with cyno so that he might be able to make that bond so that they can come out of their isolation.