Kingdom of Science[]
Senku Ishigami[]
He was initially an enemy to Senku, due to being Tsukasa's right hand man, but sides with him after learning he and Yuzuriha are repairing the broken petrified humans. Ukyo is often amazed by his efforts, though he can be surprised by his plans for inventing. He becomes one of the vital assets for the Kingdom of Science due to his perk of superhuman hearing.
Ryusui Nanami[]
Despite little interaction between them, they seem to be on good terms. They both have experience in the ocean due to Ukyo being a sonar technician and Ryusui a sailor, due to this, they were the only Perseus members who noticed Kirisame's presence before she came out of hiding.
After Senku invents the firearms, Ukyo says that he wants to avoid bloodshed and hopes that others won't think his idealism is nonsense in the dire situation they are in. However, Ryusui says that his attitude is completely logical since killing people just makes enemies of their friends and family, which is why they aren't going to kill anyone with their gun, something that made Ukyo smile.