Yuuma Kuga is one of the main protagonists of World Trigger and is a Neighbor with high Trion level and Trigger Skills.

Yuuma is very short for his age. He has white hair and red eyes. He wears a blue suit top and gray bottoms traditional of Japanese high school students. When not in Trigger mode or school uniform, he usually wears a black hoodie with a paw symbol and the text "UMA" (which stands for "Unidentified Mysterious Animal"), and baggy jeans pants.

In Black Trigger mode Yuuma gains a black jumpsuit which Replica fuses itself with. In C-Class trigger mode, unlike most other trainees, he gains an all-black uniform, instead of the classical all-white one; it has a black jacket with thick white stripes running down from the sides of his collar to the sides of his sleeves and also around his collar, and thin gray stripes in the borders of the zip fastener and collar.

In B-Class trigger mode, he has a uniform similar to Osamu's, except his jacket's left sleeve doesn't have a shoulder guard. His right arm also has the same design as his left, unlike Osamu's, making his jacket more symmetrical. Also, the black stripes on his jacket's sleeves are thinner and, unlike Osamu's, don't have white stripes in their middle, and the black stripes also go over his shoulders and collar. On the sides of his shoulders, he has Tamakoma Branch emblem, surrounded by the stripes. In addition, the sleeves of his jacket somewhat merge with his gloves, and he tucks his pants inside his boots, like when he was a C-Class agent. His Unit's emblem is located on his left chest.

Yuuma has a laid back personality and is not very knowledgable about Japanese customs, due to being from another world (despite having a Japanese father), leading to some run-ins with rough people. He is logical, advising Mikumo to stay away from the Trion Battle Soldier rather than save the students as Mikumo could die. He seems to be aligned with Border's cause, fighting against Neighbor forces. Despite his happy exterior, he is actually deeply depressed due to his father's sacrifice to revive him, and had no more reason to live for other than bringing him back to life.