Stone (2010)

Kwon Soo Baek has been teaching Chinese at school for 28 years, working diligently to support his son Jae Ho's medical school tuition. His only wish is to impart his knowledge to students and help them graduate, but his reputation for being so nice that it approaches timidity makes it difficult. When Soo Baek's superior, Yoon Jung Nam, is investigated for embezzling billions of the school's operating expenses, he is called to testify and has to decide whether to remain timid or speak out.