Rin Nohara

Rin was a medical-nin and the teammate of Kakashi Hatake and Obito Uchiha under the Fourth Hokage in the Kakashi Gaiden exclusive.

Etymology
One possible meaning of her name means "cold". More likely, however, Rin is one of the readings of the kanji hayashi,. Usually when used for a girl's name it's written with the kanji for suzu,. Which meaning her name has is unknown, other characters from Konoha have names related to trees or leaves, but bells does have a relation, the bells used in the training by both Sarutobi and Kakashi in the series.

Role In Kakashi Gaiden
She was a sweet and friendly girl who cared for her teammates. She had intimate feelings for Kakashi, but he ignored her. In turn, Obito had a crush on her but she ignored him. Similar to the relationship between Sasuke, Naruto and Sakura.

When Rin was captured by enemy shinobi from Iwagakure, Obito and Kakashi went to go save her, though it takes some prodding to get Kakashi to help.

Later, half of Obito's body is crushed by a rockslide in an attempt to save Kakashi. At Obito's request, Rin implanted Obito's remaining Sharingan eye into Kakashi's damaged left eye socket. Kakashi then vows to protect her with his life, at Obito's request.

Her status is currently unknown, but she is presumed dead as Kakashi said that everyone close to him is dead. Thus Kakashi's saying, "I won't let my comrades die."

Speculation
Some believe Rin might be a member of the Inuzuka clan because of the marks on her face resemble that which all of the Inuzuka members have. However, Rin's markings are a different color and shape to those of the Inuzuka Clan.