Japanese language files

Here is my fixed code(send-to-kindle.php):

private function __construct() {
		load_plugin_textdomain( "kindle", false, dirname( plugin_basename( __FILE__ ) ) . '/languages/');
		// Set up sensible defaults.
		add_option( 'stk_button_look', array(
			// placement
			'home' => true,
			'archive' => true,
			'post' => true,
			'page' => false,
			'before' => false,
			'after' => false,
			// button style
			'color' => 'white',
			'size' => 'small',
			'border' => true,
			'theme' => 'light',
			// button text
			'text' => 'send-to-kindle',
			'font' => 'sans-serif',
		) );
		add_option( 'stk_button_advanced', array(
			'selectors' => array(
				'title' => '.entry-title',
				'published' => '.entry-date',
				'content' => '.post',
				'exclude' => '.sharedaddy',
			),
			'enabled' => false,
			'markup' => '<div class="kindleWidget">Kindle</div>',
		) );

		// Register actions and filters.
		add_shortcode( 'sendtokindle', array( $this, 'get_button_html' ) );
		add_filter( 'the_content', array( $this, 'attach_to_content' ) );
		add_filter( 'get_the_excerpt', array( $this, 'clean_the_excerpt' ) );
		add_action( 'wp_enqueue_scripts', array( $this, 'enqueue_script' ) );
		if ( is_admin() ) {
			// Only load settings screens for admins.
			add_filter( 'plugin_action_links_' . plugin_basename( __FILE__ ),
					array( $this, 'settings_link' ) );
			if ( ! class_exists( 'STK_Settings' ) ) {
				include_once( dirname( __FILE__ ) . '/admin/settings.php' );
			}
			if ( ! class_exists( 'STK_Settings_Advanced' ) ) {
				include_once( dirname( __FILE__ ) . '/admin/settings-advanced.php' );
			}
			$settings = STK_Settings::get_instance();
			$advanced_settings = STK_Settings_Advanced::get_instance();
		}
	}

I hope you will find it helpful.