Japan, with numerous active volcanoes, has developed systems for volcanic disaster preparedness. Media coverage is vital for informing the public about volcanic risks and handling hazards. The Internet now enables people to check and share eruption risk information online. Public concerns are affected by how risks are portrayed in traditional and online media. This study examined media coverage (online news sites and TV) and online comments (Twitter and Yahoo! comments) related to Mt. Kusatsu-Shirane’s eruption in January 2018 to understand what kinds of emotional reactions were triggered in people by media. A content analysis of news articles and comments showed that volcanic risk awareness was strongly evoked when the media covered human and economic damage. Negative comments about experts and volcanology appeared independently of news context, reflecting society’s perspective on whether volcanology is useful for practical prediction. TV media focused on victims, airing episodically framed stories. Twitter comments often mirrored media contents. Risk perception of volcanoes can be enhanced when volcanic risk information disseminates to society but may fade with reduced coverage. Episodic news framing leads to victim-blaming and remembering only stereotypical victim images. This could fragment social ideas about volcanic risk management and hinder a unified approach to preventive actions.