The main antagonist in the manga Kaiju No. 8. Kaiju No. 9 is a humanoid numbered Daikaiju who goes around reviving the kaiju killed by the Defense Force. He previously infiltrated Professional Kaiju Cleaning Company Monster Sweeper.

In his fused form with an Ant-type kaiju, No. 9 has the lower part of his body replaced by an Ant kaiju which he controls and uses to move around. In this form, No. 9 lacks forearms and hands. After fusing with Kaiju No. 2, No. 9 is now much larger than before, keeping his darker skin tone, with a long tail, three sets of eyes, and only protuberance on his head instead of two.