Ultimate Detective Kirigiri (released outside of Japan as Danganronpa Zero: The Kirigiri Files) is a prequel to the original Danganronpa that focuses on the character Kyoko Kirigiri, the game was released for the PS Vita and Nintendo 3DS in 2017.
The game is split into various chapters detailing the most important cases of Kirigiri's past life before entering Hope's Peak Academy, the game takes place after the light novel Danganronpa Kirigiri.
Chapter 1 - Zero Detective
Ultimate Detective Kirigiri is a cross between Danganronpa and Ace Attorney in terms of gameplay.
You're free to roam around the area and scan specific places to look for clues or evidence, you can also interrogate other people in various different ways to get information out of them. When someone you meet disagrees with you, you go into a "Power Debate", in which you must contradict the other by using Truth Bullets (which represent information or evidence) to deplete their Truth Gauge.