Rin leaves True Cross because nobody wants him at true cross academy. Because he is the son of Satin. Even his own brother didn't want him their. But their was one who wanted him to stay. Shiemi she was the only one who supported him through all that is happening. But Rin left True cross to forget everything that happend he wants to forget everything. Shiemi was sad to see her best friend leave and she will not forgive the other exersist who did that to him.