The Union 7 is a political organization in killer7. Although based in the United States, it is actually a Japanese organization. It is the origin of the drafting of the Yakumo. Its name likely has to do with the United Nations Party, who wield the Yakumo, and their goal of a world unified under Japanese rule, although it may also reference (or foreshadow) the fact that its members were murdered at the Hotel Union by Emir Parkreiner. The murder of the Union 7 and the Second Smith Syndicate are linked events, to the point that the murder was known as the "killer7" two years before the group with the same name emerged; it is sometimes unclear if the murder of the Union party members and the murder of the Smiths are even distinct events or not.
Union 7 was originally made up of (presumably seven) young members of the Liberal Party, including Toru Fukushima, who left the party after the creation of the Yakumo. Because Fukushima is alive during the game, it can be assumed that he somehow survived the "killer7" murders.