#wpmem_register_form fieldset {
    border: none;
}

#wpmem_register_form fieldset legend {
    display: none;
}

#wpmem_register_form label[for="username"],
#wpmem_register_form input[name="username"] {
    display: none;
}

/* 牢獄完了画面のログインフォームを隠す */
.register-user #wpmem_login {
    display: none;
}