Hayama is Taro Sado's classmate and close friend. He enjoys cross-dressing (which induces his female alter-ego to appear). He is troubled at the start when Taro, who does not know of Tatsukichi's hobby, becomes infatuated with his female alter ego. His alter-ego, "Tatsumi Antoinette XVI," has superiority complex while he is cross-dressing, and repeatedly argues with Isurugi (sometimes over Taro's affection) as well as repeatedly attacking verbally Mio's breast size. He was previously in a relationship with Yuno's best friend Yumi, but states that he is unsure how he now feels about her.