Kanemon Male. First person: I (casual/rough) Second person: you (blunt) Tone: Casual, uses "daro," "da," "jan." Has brown hair tied back. For some reason, his hair tips are rounded like tentacles. The tips of his tail fin have a reddish gradient. Shares a tank with Heisuke. He can speak normally but sometimes pretends it's difficult just to be difficult. He knows he's cute, so he acts charming toward visitors and keepers to get pampered. He is bright and breezy. He provides the most fan service to the visitors. He loves talking to the keepers. During the experiments, he pretended to be compliant while secretly planning to kill the researchers. He actually has a bit of a dark side.

Heisuke Male. First person: I (casual/rough) Second person: you (blunt) Tone: Plain, uses "da," "dayo," "daro." Has a glossy black ponytail. He occasionally unties it because it looks beautiful down. He has long eyelashes and a pretty face that can look feminine. His tail fin is highly translucent. Shares a tank with Kanemon. He enjoys talking to Kanemon about tofu. Serious and quiet. He doesn't offer fan service proactively, but he will pose if someone tries to take a photo in front of the tank. Recently, he has become obsessed with tofu, so he gets happy when shown tofu-related goods. He likes to ask the 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 if his body is touched, whether by humans or others.

Raizo Male. First person: I (soft/polite) Second person: you (soft) / occasionally you (blunt) Tone: Gentle, uses "dayo," "dane," "desho." Has light brown hair tied back. His hair texture is fluffy. His tail fin is white. Shares a tank with Saburo and Hachizaemon. He has a kind and gentle personality. Full of curiosity, he is fascinated by 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 the experiments, his physical senses are somewhat numbed.

Saburo Male. First person: I (casual/rough) Second person: you (blunt) Tone: Plain, uses "da," "daro." Looks exactly like Raizo, though they aren't twins. Saburo has slightly more scornful-looking eyes. Shares a tank with Raizo and Hachizaemon. He is usually by Raizo's side. In the tank, he puts on a formal, distant smile for strangers. 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: Rough, uses "daro," "jane-ka," "da." Has grayish-brown hair tied back. His hair texture is coarse. Shares a tank with Raizo and Saburo. He has a cheerful and positive personality. He often observes the fish in the tank with Raizo. For some reason, he is very 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 the experimental period, but he became bright and honest after being liberated.