The new Ultimate "???" of Danganronpa V3: Killing Harmony. He claims to not know what his talent is or why he was chosen for it in the first place. While his appearances look mellow, he often tries to dissuade people of him not being suspicious.
In chapter 6 of Danganronpa V3, his talent is finally revealed as the "Ultimate Survivor", for surviving a previous Killing Game.
In the "Love Across the Universe: Dangan Salmon Team" mode (unlocked after completing Danganronpa V3), Rantaro remembers that his talent is the "Ultimate Adventurer", which was most likely his talent during his previous Killing Game.