The (Not so)Secret Society of Seijins are the archenemies of the Ultra Brothers in Ultra 101. I know most of your are probably already familiar with them, but here's a recap.
The original Baltan that Shin(Ultraman) fought, and the now last surviving of his colony. He is very enthusiastic and oriental, with a hard Japanese accent and an "Engrish-y" speach pattern. He was the founder of the Society, and the leader until Djent came. His primary enemy is Shin.
A Gutsian business man. The business? Strategies. I know, it sounds weird. He sells battle plans, but currently he's in a contract with the Society, so he can't make deals with anyone else. He commonly ends up fighting Seven.
A Knacklian hitman who is obsessed with killing Jack. All he can say is variants of "Kill Jack!!!", so he has been given the nickname "Kill-J", as no one is aware of his real name. Take a guess who he fights the most among the Ultra Brothers.
An old cranky Valkian fisherman. He's not necesarrily evil, but he can be very dangerous. Taro killed what would have been the biggest catch of the year, so he's sworn vengeance.
No name, no background information. Just... The Dada.
A galactic swordsman who peppers his speach with Japanese. He is always hyper for a fight. He was recruited later in order to match Mebius. While initially not interested in Mebius, he inadvertently lead him to unlock his Mebium Blade, and he now sees him as a challenge.
A very unenthusiastic Batian. He doesn't have much personality, other then acting vaguely creepy. He was recruited to fight Zero, though they don't have any reason to be arch-enemies.
The mastermind, a Mefilisian criminal. Initially, he was just a big mafia boss, but he decided to up his game upon learning of the Society. He quickly took over the sorry bunch, and turned into into a formidable force. He can be a little nutzy at times.