>>75730045They didn't "allow" him to graduate, they were forced to let him graduate. His contract expired and he chose not to extend it.
He's been on hiatus ever since they suspended Selen. In all likelihood, he turned in his resignation notice as soon as they terminated her.
There are very, VERY few lines of employment where an employee can be hit with an involuntary and indefinite contract extension. Unfortunately for Riku, vtubers are not one of those very, VERY few lines of employment.