Toru Ishikawa has dreams where his friends appear as half-animal, half-human versions of themselves. These are recurring dreams, and though he never explicitly tells any of the characters about them, he is influenced by what happens in his dreams. For example, after Myamura expresses his love of milk in his dream, Ishikawa goes and buys a ton of milk for the real life Miyamura.
Aside from Ishikawa himself, all of the other characters come in 3 sizes: small, medium, and large. It is generally thought that each size represents a different age, with small being kindergarten, medium being late elementary school, and large being high school. The characters' personalities also changes depending on their size, though fundamentally, they retain their real life personality. Except for a few special cases, a character will only appear in 1 size per dream, and them appearing as a new size indicates the start of a new dream.
Toru Ishikawa Edit
Ishikawa himself. He is his normal self. He acts as the other characters' guardian, and spends most of his time taking care of the others (usually the small and medium ones). He seems aware that everything is a dream.
Myamura (Izumi Miyamura) Edit
A half-cat version of Miyamura. He tends to be more selfish than his real-world counterpart. He loves milk. Small Myamura appears the most often, and has a very child-like and innocent personality. He is most commonly paired with medium Nyangoku, who acts as the mature one in the pair. Medium Myamura is very self-centered, often times asking for extravagant things. Large Myamura is almost identical to his real life self, though he doesn't make many appearances.
Nyangoku (Kakeru Sengoku) Edit
A half-cat version of Sengoku. He tends to be serious and mature, like his real-world counterpart. Due to this, he usually ends up acting as an older brother to Myamura. Also, just like his real-world counterpart, he is a chicken, scared of both Horineko and Yukicchu. Small Nyangoku is more mature than small Myamura, and is similar to how Okuyama is with Souta. Medium Nyangoku appears the most. He acts very mature, often times trying to keep Myamura in line. He's also much kinder than normal, usually quietly giving way to Myamura's selfishness. Large Nyangoku, on the other hand, is much harsher than normal, usually scolding Ishikawa for even the slightest infraction.
Horineko (Kyoko Hori) Edit
A half-cat version of Hori. She appears far less than Myamura and Nyangoku. Due to the fact that she's female, the other two tend to stay away from her, though their large versions have no such aversion. She's very aggressive towards Yukicchu, as she takes her role as a cat very seriously. However, since Ishikawa does not allow her to harm Yukicchu, but Yukicchu usually still bites her ears, Horineko is usually at a loss about what to do. Small Horineko is rather quiet, and just wants to play with the others, though this often proves to be difficult. Medium Horineko is sterner, similar to how her real-world counterpart acts towards Ishikawa. Large Horineko is even more aggressive, willing to strike Ishikawa if she thinks he is going to do something to her.
Yukicchu (Yuki Yoshikawa) Edit
A half-mouse version of Yoshikawa. She was not introduced until much later, but quickly became a regular character, right behind Myamura and Nyangoku. She loves to bite things, especially Nyangoku's tail, Horineko's ears, and cushions. Even though Ishikawa frequently reprimands her for her biting, she can't control her instincts and continues to bite things. Even though the others are cats, Yukicchu is the aggressor. Horineko is the only one who stands up to her, but since Ishikawa won't let her hurt Yukicchu, eventually she too has to run and hide from Yukicchu. Small Yukicchu is the most whimsical, going around and biting everything without restraint. Medium Yukicchu knows that she shouldn't bite things, but after seeing how delicious looking their tails or ears are, she can't control herself and bites them anyway. Large Yukicchu has the most restraint, constantly telling herself not to bite things. But in the end, even she succumbs to her desires and bite them.
Yanyangi (Akane Yanagi) Edit
A half-cat version of Yanagi. He appears the least. He is very mature and gentle. He likes playing with blocks, and will usually get the other cats to play with him. In his larger versions, he also tries to comfort and console the others, as well as play with them.
Mentioned by the author, but has not appeared in the comic yet. Most likely the half-cat version of Shu Iura.