Rin has an extremely compassionate and supportive personality. He can be very violent and get into fights , but in truth, has a kind heart.
He supports his friends and tries to encourage and help them in any way possible. He is also very protective of his brother and aims to surpass him one day.
However, Astaroth often finds Rin annoying due to his frequent impulsiveness, stupidity and his care-free attitude. (Astaroth still thinks highly of Rin)

Although he generally hides it, Rin loves his father a great deal and has nothing but good things to say about him. Much like Astaroth, he takes any insult against him very seriously.
He also doesn't like people insulting Astaroth, whom he eventually started to like and greatly respect.
Besides this, however, Rin is surprisingly even-tempered and laid-back and rarely gets angry without a good reason.

Rin is often shown to be able to relate to people easily and connect their feelings to his own. In general, he is often the first one to try and make people feel better if they're down.
He's not the type of person for school or studying, though he was able to gain a hunting and tracking diploma.

Unlike his brother, Rin is immature, which leads other people into believing that he is younger than Astaroth;
it's been noted by several pack members that despite being half brothers, he and Astaroth couldn't possibly be more different. He is headstrong and often very open with his friends.