Kaiju are monstrous creatures that come in different sizes and shapes. All of them have different features, some more humanoid than others. Every kaiju posses a core, which is their vital organ and weakness, inside their body, and since every kaiju comes in a different type the location of the core changes accordingly.
Most Kaiju shown in the manga seem to have no eyes. But even so, they are still able to locate targets. Their teeth are usually visible and they come in different shapes such as regular human teeth or sharp and pointy teeth.
Powers and Abilities
All kaiju possess different abilities and powers, so it's quite rare to find similar kaiju. Every Honju (the strongest in a group of Kaiju) is given a fortitude number, which is a way for the Defense Force to measure a kaiju's power and its potential threat to humanity.
Some powers most kaiju have in common are super strength, proliferation abilities, and great fortitude levels. Some of them are able to fly and the most complex is even able to practice human language and, through that, talk.
Daikaiju (大怪獣, Daikaijū, lit. "Large Monster") also known as "Mega Monster", is the name given to particularly strong kaiju, whose fortitude level exceeds the number 8.0. These kinds of kaiju are part of the strongest category, with their power not necessarily being linked to their size, since Kafka, who has a fortitude level of 9.8 in his kaiju form, the highest seen thus far in the series, defeated kaiju much larger than himself in his kaiju form. Due to their incredible power, daikaiju can also be honju and guide their group of yoju (like Kaiju No. 10 with the wyvern kaiju); but also because of their might, daikaiju are not above operating individually on their own. According to Isao Shinomiya, the Defense Forces presently have around two dozen elite officers who stand a chance at taking on a daikaiju, less than ten in single-combat and when fighting a numbered monster, the number gets even lower.
A Honju (本獣, Honjū), also known as "Base Monster", is usually the biggest kaiju, the most powerful, and the one who generates and guides all the other yoju through their proliferative organs. Their fortitude level is usually above 6.0. A honju with a fortitude level of 6.4 would require an entire platoon of Defense Force soldiers to defeat it, and only a captain or vice-captain could defeat it alone.
A Yoju (余獣, Yojū), also known as "After-beast", is a smaller kaiju who accompanies their honju. There are usually numerous yoju to assist a honju. Some kind of Yoju can have proliferative organs like the honju. yoju can appear in many ways, by traveling routes made by honju, leeching onto honju, being created by honju, and more. Some yoju can have a fortitude number above 6.0, thus being a honju-level threat while still being a yoju.
Anatomy: They have a violet human-like body with a long spiked tail and hoofs at the end of their fingers and feet. Their head features a large mouth with jagged square teeth and no eyes. While the Honju has two bull-like horns, the various Yoju an elongated cranium. These kind of kaiju have a hyperdeveloped sense of hearing, compensating for their poor vision, which makes them vulnerable to stunning attacks. Furthermore, their skin is thinner on the underbelly than the rest of their body.
Anatomy: Fungal-types are kaiju with a round and stocky body and a peculiar no-eyed head shaped like a mushroom cap. Located in their near end, even the Yoju have reproductive organs, allowing them to spawn others of their kind from their own corpses. Their core is located in the neck, under the hard-fiber muscles that act like a spine, although Kafka Hibino noted that such spot isn't the usual place where the core should be located. It was then revealed that the core's unusual position was a modification made by Kaiju No. 9.
Plot: A pack of Fungal-types attacked Sagamihara but they were subsequently defeated by the Third Division.
Anatomy: Wyvern-types, as the name suggests, have the shape of dark orange pterosaur/dragon-like reptilian, possessing big wings, a long tail, a horn on their head and six red eyes, as well as the ability to spit flames and to fly up until 8000 metres above the ground. On the frontal part of their body, they tend to have tougher skin to act as a shield while they are flying, whereas the skin of their back has a minimal coating to decrease the weight, making it their weak spot. Wyvern-types have shown the ability to fuse with one another to create a massive flying Yoju-bomb out of the bodies of all the Yoju, able to detonate when touching the ground.
Behavior: As noted by Kafka Hibino, due to their immense sense of pride, all Wyvern-types share the habit of acting alone, meaning that seeing them as a pack is quite rare, although they seem to respond to sonar waves. For these reasons a kaiju as strong as Kaiju No. 10 can easily command them.
Plot: Ever since 2003 about only ten Wyvern kaiju were reported every year. A pack of Wyvern-types, guided by Kaiju No. 10, attacked Tachikawa Base and the Third Division. Then, in the climax, they fused together as a Yoju-bomb but detonated in the sky thanks to Kaiju No. 8's intervention.
Anatomy: Ant-type kaiju are massive ant-shaped kaiju with a light-colored spotted body and massive abdomen. They have the power to secrete an acid liquid from their mouth and antennas.
Behavior: They usually travel in packs. According to First Division Captain Gen Narumi, there are rare occasions to encounter ant-types in tunnel construction work and it's even rarer to see them appearing on the surface, especially in great numbers. This kind of kaiju would also follow the orders of a leader strong enough to command them, like Kaiju No. 9.
Plot: A pack of Ant-types, lead by Kaiju No. 9, attacked Shinagawa but they were quickly defeated by the First Division.
Anatomy: This specific kind of Mole-type kaiju presents a stocky quadrupedal shape, with its face shaped like that of a talpidae with sharp teeth and two sets of vertical narrow long eyes. The Honju has a Resilience of 6.4 and, unlike the Yoju, is much bigger than the others and possess a large spiky collar.It can also spawn spikes on his body and can shoot energy beams from his mouth.
Behavior: This kind of kaiju appears to be rather aggressive in its own territory, as well as holding on to the same habit for a long period and with a systematic rhythm over time.
Plot: According to Fourth Division Captain Jugo Ogata, after its first appearance in 1967, from which it takes its name, the kaiju kept reappearing every five years in the Bunguitoge pass mountain zone. The Mole-Type 67 was targeted by the Fourth Division as a test subject for Leno Ichikawa and his Numbers Weapon 6. All the Yoju and the Honju were neautralized by Ichikawa himself.
Numbered Kaiju are uniquely strong kaiju, or Daikaiju, who prove remarkably difficult to neutralize by the Defense Force. For this reason, the Neutralization Bureau gives them numbered codenames in order to identify them.
Up until know only ten numbered daikaiju appeared in history: