Haitatsu sarenai santsu no tegami

Noriko's fiancé Fujimura has been missing for three years, so she shut herself up in her room. Suddenly, Fujimura came back accompanied by his sister, Tomoko. They got married right after. But, Noriko's sister, Keiko and her cousin found three letters that was written by Fujimura to Tomoko. On these letters, the plans to murder Noriko were written. (Shochiku)