How are the characters connected to the original game in Danganronpa:UDG?
A lot of the links can be found if you go on the wiki. The targets were all the most important person to their corresponding character from the first game.
For Example, Hiroko Hagakure is Yasuhiro Hakagure's mother, and Yuta Asahina is Aoi Asahina's brother. But, not all of these figures are human. Celestia Ludenburg's most important person was her cat, and Touko Fukawa's was a bug.