Recent advances in technologies for neuroscientific research enable us to investigate the neurobiological substrates of the human ethical sense. This article introduces several findings in "the brain science of ethics" obtained through "brain-observation" and "brain-manipulation" approaches. Studies over the past decade have revealed that several brain structures associated with emotion processing and the ability to understand the minds of others play key roles in the human ethical sense. We also discuss current limitations in studying the brain mechanisms of ethics: Although the true significance of the human ethical sense lies in social interactions, most neuroimaging studies so far have not captured the rich context of the social interactions that exist in the real world. The latest experimental paradigms focusing on "neural resonance" across brains, as well as a newly developed neuroimaging instrument that allows a wide range of social interactions under natural situations, are promising to overcome this limitation. Applications of such approaches and instruments to study the human ethical sense will improve our understanding of the complex nature of the human ethical sense.