amazon_target_killer.user.js

// ==UserScript==
// @name              Amazon target killer
// @namespace         http://tech.portalshit.net/
// @description       Kills `target="_blank"` on search result screen
// @author            morygonzalez
// @version           0.3
// @include           http://www.amazon.co.jp/*
// ==/UserScript==

var targets = document.evaluate('//h3[contains(concat(" ",@class," "), " newaps ")]/a | //div[contains(concat(" ",@class," "), " imageContainer ")]/a', document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null)
for (var i = 0, len = targets.snapshotLength; i < len; i++) {
  var link = targets.snapshotItem(i);
  link.setAttribute("target", "_self");
}