Completely out of character for every single character portrayed.
Ranma has never had any particularly strong sense of duty. He would not, and does not, stick around in canon out of obligation. He could easily pack up and leave any time he wants, as the regular training trips he's shown taking in canon shows.
(Akane's also incredibly ooc, she's as stuborn as Ranma and would stick with things out of sheer stubbornness.)