Tamaki is Haruka Murakami's boyfriend whose act of infidelity devastates her emotionally. This betrayal becomes the catalyst for Murakami's subsequent actions and shapes her dynamic with Misuzu Moritani. Following the discovery, Moritani urges Murakami to exact revenge. This results in Tamaki's sole narrative appearance: a confrontation engineered by Murakami and Moritani to publicly humiliate him within a lingerie store. His role is confined to this incident of betrayal and its direct consequences.