"Side Story 3: A True Hero" (外伝其ノ三:本当の英雄, Gaiden Sono San: Hontō no Eiyū) is chapter 241 of the original Naruto manga.
Their master leaves Kakashi, Obito, and Rin to destroy the Kannabi Bridge by themselves while he goes to assist Konoha's forces on the frontlines. The three try to travel through Kusagakure in secret but are found by enemy ninja looking for the ninja the team encountered earlier. They kidnap Rin to see what she knows. Obito immediately tries to go after her, but Kakashi stops him, saying they must complete their mission first as the Shinobi Rules dictate. Obito lists a number of reasons why they should place saving a team-mate above the mission's success, but Kakashi is unmoved. Obito leaves, saying that those who abandon their friends are scum. He also says that Sakumo Hatake, despite being disgraced when he abandoned a mission to save his team, was right to do so.