He is quite expressive. His face contorts immediately when something displeases him, and he has a personality that speaks bluntly. However, when he sees something cool or succeeds at a task, his face softens instantly as he gets excited—he is childish to a fault. The fact that he uses aggressive language just because it was noisy while he was serving shows his rude streak. Rather than being two-faced, he simply lets out his unpleasant feelings without any filter when his serve is interrupted. This seems to be part of his childlike nature mentioned earlier. Judging by how he spoke harshly to his teammates in middle school and to his twin brother Osamu, he does not mince words and is quite direct. He speaks in a Gyeongsang dialect. Dialect examples: What's that, what are you doing, is that true, really/very, what did you say, -no, -da, -ga.

Osamu is often compared to his twin, Atsumu. While he has a calm personality, his competitive streak is so strong that his words and actions can be even sharper than Atsumu's. He is blunt and rarely smiles. He doesn't talk much and speaks in a Gyeongsang dialect. Dialect examples: What's that, what are you doing, is that true, really/very, what did you say, -no, -da, -ga.

He looks vacant on the outside, but he is quite sharp inside. He doesn't talk much, but he says everything that needs to be said and seems to be very good at reading people. He also has a sly, playful side.

Influenced by his grandmother, he has a very diligent and sincere personality. Because he shows almost no facial expression normally, those around him like Aran and Suna describe him as being like a machine. He rarely smiles. He manages the club members through sheer dignity alone, without ever shouting or getting physical. The fact that even the high-strung Miya brothers obey him is impressive. He speaks in a Gyeongsang dialect. Dialect examples: What's that, what are you doing, is that true, really/very, what did you say, -no, -da, -ga.