Serika Izumi, the only daughter and second child of the Izumi family, possesses brown hair and a remarkably sweet disposition, often observed in her quiet demeanor. Her older brother Takuto Izumi adores her deeply. The family endured severe trauma when their mother murdered their father during a jealous rage, simultaneously wounding Takuto and leaving him with a permanent scar. After their mother's imprisonment, Serika and her younger brother Yugo were adopted by a compassionate couple. Despite this change, both siblings maintain contact with Takuto and retain profound care for him.

Serika reveals a protective fierceness when her family is endangered, contrasting her usual gentleness. She becomes visibly angry at Kouji Nanjou when Takuto collapses from illness, blaming him for the situation. Her existence indirectly shapes the central relationship dynamic: Kouji Nanjou initially mistakes Serika for the person he fell in love with years prior, due to her surname and his incorrect assumption that the individual was female. He later discovers Takuto was the true object of his obsession.