It could just be luck, honestly. Jack is too deep into his thoughts to really remember other people's names, which would be an issue, considering he'll come off as rude, but it's really just the Reviars sucking at names (although actually, Jack does remember Kenji's name, so that's invalid). Anyway, I want Kirishima to choose Kenji. Jack doesn't care who it is as long as they promise to do everything in their power to protect Sylvia.