Hikaru Toma is the central protagonist of Izumo. He is a young man who was raised by his grandfather, Rokusuke Toma, alongside his sister, Miyuki Toma, after his parents died when he was very young. The three live together, and Hikaru attends Izumo Academy, an institution run by his grandfather. His life takes an unexpected turn when he discovers a hidden shrine-like structure on the school grounds, an event that leads to him being summoned to Ne no Kuni, the underworld.

In terms of personality, Hikaru is characterized by a somewhat contradictory nature. While he can be lazy in his daily life, he is notably diligent when it comes to practicing swordsmanship. He possesses a gentle and kind disposition, which, combined with his handsome features, naturally draws the attention and affection of several female characters around him. He is largely unaware of the deeper feelings his sister Miyuki holds for him, as he does not know they are not related by blood.

Hikaru's core motivation is deeply intertwined with his true origin. He is not an ordinary student but is, in fact, the son of Izanami, a goddess of creation. Izanami created a child using the power of dreams as a means to stop Yomotsu Okami, a malevolent entity born from her own accumulated hatred and sorrow. This child was Hikaru, who was sent to the human world alongside the children of other priests to be raised by Rokusuke Toma, who is later revealed to be Izanagi, a god and the father of Izanami. Therefore, Hikaru's journey to the underworld is not a random occurrence but a destined confrontation with a corrupted aspect of his own mother.

Within the story, Hikaru serves as the leader of the group summoned to Ne no Kuni. His role is to battle the forces threatening the balance between worlds and ultimately face Yomotsu Okami. His key relationships include his sister Miyuki, a childhood friend and underclassman named Nanami Mizuse, a self-proclaimed rival named Nagisa Kurashima who practices western fencing, and an elder sister figure named Kyoka Tachibana. He also encounters a mysterious girl named Amaterasu, who is connected to his destiny.

Throughout the narrative, Hikaru develops from a somewhat lazy student into a warrior who accepts his profound and tragic destiny. His true heritage is revealed over the course of his journey, forcing him to understand that his purpose is to defeat a part of his own mother. In the conclusion of the original game's true ending, Hikaru chooses to remain in the other world alongside Amaterasu to act as its protector, taking on the name and role of Kagutsuchi. The original game establishes that he continues to be active after the events of the first story.

In terms of abilities, Hikaru is a skilled swordsman, having trained in iaido, the Japanese art of fast sword drawing, at his grandfather's dojo. He frequently tests his skill against Nagisa's fencing, making combat a regular part of his school life. In the world of Izumo, his fighting style is characterized by swordsmanship with a fire attribute.