Amakusa Sayo (birth name: Mutoh Sayo) is younger sister of Amakusa Shōgo and maternal niece of Nishida Hyōei. She preached under the name Magdalia, but suffered from an illness (later determined to be tuberculosis by Kenshin). She realised what her brother was doing was wrong, but was shot trying to save Doctor Elsten before she could stop him. She seemed to be falling in love with Sagara Sanosuke, and entrusted her will to him, so that he could give it to her brother and soon afterwards she died in his arms. In the will she spoke of her father's teaching that a man's value is not determined by his wealth or his class, but by his piety and kindness. She then spoke of her dream to liberate the oppressed Christians of Shimabara, but that she was unable to live this dream, due to her death and so wanted her brother to fulfill her desire.
Sayo has a very kind personality and teaches her followers to always trust and believe in God and to be kind to others, even their enemies. Though she initially believes outsiders (i.e. non-Christians) to be wrong-doers wishing to inflict harm on Christians, she later drops this idea, after learning of Sano's concern for her and her people.
Amakusa Sayo, was a young woman of average height and weight, with fair skin, long, wavy, medium brown hair and wide green eyes. Sayo, usually wore her hair loose.
Her main outfit was a white dress with long sleeves, with pink outlined red fabric at its ends with a red undergarment beneath the white dress. She also wore a pink and red cloak, with a lime green cape, red shoes and a medallion around her neck, which consisted a silver metal piece, with a symbol of her Christian Belief, engraved on it, attached to a necklace of purple pearls. Sayo also wore long, circle shaped green jewel earrings on her ears complementing her green eyes.