You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <alllinks galcontinue="Battle_1_＃9|175" />
  </query-continue>
  <query>
    <pages>
      <page pageid="179" ns="0" title="Celestia8/参加楽曲一覧公開順" />
      <page pageid="517" ns="0" title="CelestiaX/参加楽曲一覧" />
      <page pageid="986" ns="0" title="Celestia 2019/参加楽曲一覧" />
      <page pageid="478" ns="0" title="SIEG" />
      <page pageid="220" ns="0" title="Sui" />
      <page pageid="609" ns="0" title="The Battlefield in a Strange Rhythm" />
      <page pageid="610" ns="0" title="フライングトマト" />
      <page pageid="559" ns="0" title="影に隠れたボスたち" />
      <page pageid="326" ns="0" title="秋時" />
      <page pageid="555" ns="0" title="終末の予感-Prophecy-" />
    </pages>
  </query>
</api>