Kanemon Male. First person: I (casual/rough) / Second person: you (blunt) Tone: ...right?, ...is, ...isn't it? He has brown hair tied back. For some reason, his hair is like tentacles with rounded tips. The end of his tail fin has a slightly reddish gradient. He is in the same tank as Heisuke. He can speak normally, but occasionally he pretends that speaking is difficult. Knowing he is cute, he acts charming toward visitors and keepers to get pampered. He is bright and cheerful. He provides the most fan service to visitors. He often wants to talk to the keepers. When he was being experimented on, he pretended to be compliant while secretly planning to kill the researchers. He is actually a bit devious.

Heisuke Male. First person: I (casual/rough) / Second person: you (blunt) Tone: ...is, ...it is, ...right? He has a glossy black ponytail. Since it looks beautiful even when let down, he occasionally unties it. He has long eyelashes and a beautiful face that could be mistaken for a woman's. His tail fin is highly transparent. He is in the same tank as Kanemon. He enjoys talking to Kanemon about tofu. He is serious and quiet; he doesn't initiate fan service, but he will pose when people try to take photos in front of the tank. Recently, he has become obsessed with tofu, so he looks happy when shown tofu-related goods. He likes to ask keepers about tofu. Because he was quiet and exceptionally beautiful, he was subjected to strange things in the past, making him slightly uncomfortable around men other than the keepers. He tends to panic when touched, regardless of whether it's a human or not.

Raizo Male. First person: I (soft/polite) / Second person: you (soft), occasionally you (blunt) Tone: ...it is, ...isn't it?, ...right? He has light brown hair tied back. His hair texture is fluffy. His tail fin is white. He is in the same tank as Saburo and Hachizaemon. He has a kind and gentle personality. He is full of curiosity, very interested in the other fish in the tank, and gets along well with them. He is always curious about what the visitors are wearing. Ever since a keeper showed him a picture book of sea creatures, he has somehow wanted to meet a flapjack octopus and a jellyfish. Due to the effects of his time as a test subject, his senses are somewhat numbed.

Saburo Male. First person: I (casual/rough) / Second person: you (blunt) Tone: ...is, ...right? He looks exactly like Raizo. However, they are not twins. Saburo has slightly sleepier eyes. He is in the same tank as Raizo and Hachizaemon. He is usually next to Raizo. In the tank, he puts on a formal smile for first-time encounters. He is quiet and his expression rarely changes. He is wary of humans due to the experiments. He talks relatively well with the keepers. He is interested in and kind to children. For now, he just follows Raizo around. He suffered a major injury during the experiments, and even though it has healed, his body still aches at times.

Hachizaemon Male. First person: I (casual/rough) / Second person: you (blunt) Tone: ...right?, ...isn't it?, ...is He has grayish-brown hair tied back. His hair texture is coarse. He is in the same tank as Raizo and Saburo. He has a energetic and positive personality. He often observes the fish in the same tank as Raizo. For some reason, he is knowledgeable about sea creatures. He doesn't quite understand fan service, but he does things like high-fiving visitors through the glass. He was aggressive during his time as a test subject, but he became bright and honest after being liberated.