Omoi is a shinobi from Kumogakure, the Hidden Cloud Village, who first appears during the events of Naruto Shippuden as a member of Team Samui, serving alongside the team's captain Samui and his fellow teammate Karui. Along with his teammates, he was trained by the village's jinchūriki Killer Bee. He is recognizable by his dark skin, short spiky white hair, dark eyes with upward-curving lines at the corners, and the ever-present lollipop he keeps in his mouth. He carries a sword strapped to his back over the standard Cloud flak jacket, reflecting the swordsmanship tradition common among Kumogakure shinobi.

Omoi's defining personality trait is his extreme caution. He prefers to think situations through thoroughly before acting, and this tendency often causes him to become lost in his own thoughts. He is more level-headed and calmer than his quick-tempered partner Karui, but he possesses a vivid imagination that frequently leads him to exaggerate the likely consequences of even ordinary events. Karui often calls him a pessimist, particularly when he voices his worst fears about Killer Bee's safety. Despite his overly careful nature, Omoi can snap into focus instantly when a situation demands composure and decisive action. He is loyal to Kumogakure and devoted to his comrades, willing to risk his own life to protect them and complete a mission, and he remains composed even in the face of death. He shows respect for people who keep their word, even when they are enemies, and he was moved to intervene directly when he witnessed the Akatsuki forcing Sai to fight his own brother, an act that filled him with genuine disgust. Though he treats leadership with a degree of skepticism, he follows orders and keeps his personal feelings largely to himself.

Omoi's motivations are rooted in duty and loyalty. He takes his responsibilities as a shinobi seriously and is committed to safeguarding his village and the people around him. His respect for personal conviction is also strong; although he harbored anger toward Sasuke Uchiha for abducting Killer Bee, he personally acknowledged Naruto Uzumaki's determination to refuse betraying Sasuke even when doing so would have been the easier course. In the aftermath of Killer Bee's apparent capture, Omoi, Samui, and Karui were sent to Konoha to deliver a message from Bee about the Akatsuki, which served as his introduction to the story's main events.

During the Fourth Shinobi World War, Omoi was assigned to the surprise attack division under the command of Kankuro. On the battlefield he faced reanimated enemies from the past, including Sasori and Deidara, as well as Sai's brother Shin, who had been forced to fight against the Allied Shinobi Forces. In these engagements Omoi demonstrated resourcefulness and quick thinking, working effectively with allied shinobi such as Kankuro and helping to rescue comrades who had fallen under enemy control. He also received a portion of the Nine-Tails chakra cloak that Naruto distributed to the Allied forces, granting him additional protection and power during the war.

After the war, Omoi rose in rank and standing. He was promoted to jōnin and eventually became a close aide and bodyguard to the Fifth Raikage, Darui, as well as a member of Kumogakure's upper leadership. His career continued into the era of the next generation, where he remained active as a trusted figure within the village. His development over the series sees him grow from an overly cautious chūnin prone to imagining worst-case scenarios into a dependable jōnin and senior advisor, even as he retains his thoughtful and slightly anxious nature.

In terms of abilities, Omoi is a highly capable and intelligent fighter with exceptional speed, able to traverse the battlefield in the blink of an eye, and his taijutsu blends fluidly with coordinated team movement. His primary nature transformation is Lightning Release. He can channel electric chakra into his sword to strengthen his attacks and even neutralize explosive techniques, and he can hurl powerful bolts of lightning at enemies. He is also able to combine his lightning chakra with that of allies; one such coordinated technique, used by Omoi with a group of shinobi, involves converging their weapons at a single point to release an extremely wide-ranging electrical discharge, which becomes even more effective in humid or watery conditions. He can use the Shadow Clone Technique to create tangible duplicates that can fight independently and relay their experiences back to him upon dispersal, and a Lightning Release variation of the shadow clone allows him to leave a clone that reverts to electricity and paralyzes an opponent on contact. His swordsmanship consists of several Cloud-style techniques, including a reverse slash that spins his body to strike a target behind him, a deceptive horizontal slash that makes an opponent believe they have been cut, and a crescent moon slash that sends a large cutting wave at the enemy. He has also developed his own personal style, including a hidden blade technique that keeps opponents uncertain of when the strike will come, and a refined version shaped with Killer Bee's advice in which a failed attack is followed by two shadow clones so that the enemy is pressured from three directions and driven into the air, leaving them vulnerable to a falling thrust from the main body. He is additionally skilled in a high-speed movement technique that allows him to instantly close distance with an opponent. Taken together, his combination of lightning jutsu, shadow clones, and expert swordplay makes him a flexible and dangerous combatant who can adapt to nearly any battlefield situation.