Conversation so far:
when did onizawa depart from One Ok Rock?
In May 2009, it was announced that One OK Rock would continue on without Alex, who went back to the United States.
why did Alex Onizawa go back to the US?
Alex was arrested for groping the leg of a twenty-one-year-old female student on a train. He admitted to the charges and the case was settled out of court.

Question: who took his place?
Self-contained rewrite: who took Alex Onizawa's place in One Ok Rock?