Nariaki Utsumi

Nariaki Utsumi (内海 成彰) is the assistant of Gentoku Himuro at the Touto Institute of Advanced Matter Physics. He is also an aide to the Prime Minister of Touto and a former member of Faust.

He is later used as a decoy in order to hide the true identity of Night Rogue (ナイトローグ) during Touto's operation against Faust, before being gunned down by Gentoku himself. However, he was saved by Soichi Isurugi and is working with Nanba Heavy Industries.

Character History
Utsumi is first seen reporting to Gentoku about Sento's application for a job at the Touto Institute of Advanced Matter Physics, noting that Sento had passed the entrance test with a perfect score.

Utsumi is Sento's direct superior at the Institute, reporting directly to the Prime Minister of Touto, Taizan Himuro, while at the same time also secretly assisting Gentoku/Night Rogue within Faust. He was one of the first present witnessing Taizan's collapse, after the Pandora Box was stolen from the Institute. The Box was later hidden within a secret basement at one of Nanba Heavy Industries' laboratories.

Faust's Pandora Box Plan
Shortly after the emergence of a second Kamen Rider, Utsumi was called upon by Jusaburo Nanba for a favor. Later, as he watched Sento return to work despite it being a day off for all lab staff, Utsumi decided to reveal the location of the Box's hidden location to Sento. Though, the Box ended up being reclaimed by Blood Stalk, and Utsumi was eventually forced to cooperate with Nanba in his plan: to assume the identity of Night Rogue as a decoy in a staged operation by Touto to supposedly take down Faust. Due to Build's intervention, Utsumi was seemingly exposed as Faust's creator, though Build suspected that something was amiss.

Chased by Build to a bridge above a river, Utsumi, at his wits' end, confessed his inner troubles as a scientist. Revealing that he already knew that Build was Sento for a long time already, Utsumi urged Sento to not land into the same fate as his, and warned him to 'turn back' when he still have the time before he was shot in the shoulder by Gentoku, causing Utsumi to fall into the river below to his apparent demise.

Return
"It's been a long time, Mr. Himuro."

- Utsumi's first word when meeting formor superior

However, he survived and was pulled out of the river by Blood Stalk. He now works at Nanba Heavy Industries and greeted his former superior, who was waiting for Jusaburo Nanba.

On Stalk's orders, Utsumi went to Nascita where Sento Kiryu was surprised to see him alive as well as being able to make vastly superior coffee to Soichi Isurugi. Taking him underground, Utsumi revealed his intent to continue Sento's training to master the new Fullbottles left to him by Stalk in preparation for his deciding match against Kamen Rider Grease. Though Sento performed efficiently against simulated Smash Hazards with basic Best Matches, Utsumi pointed out that he would have to use the Hazard Trigger to defeat Grease. Sento understood this, and had already designed blueprints for a device which would cancel his transformation should he go berserk, but needed data of his Hazard Form's performance to complete it, to which Utsumi obliged by transforming into Night Rogue once more, using his self-made Transteam Gun from Gentoku Blueprint. Though he overwhelmed by SmaphoWolf Hazard as Build gone berserk, Utsumi was able to complete the dangerous procedure by using holographic Smashes to distract the rampaging Build, allowing him to forcefully pull out the Hazard Trigger and cancel Sento's transformation. With the data he needed collected, Sento was called away to intercept an attack on a Fullbottle facility.

Working on behalf of Nanba, Utsumi updated the Kaiser System originally developed by the late Kaisei Mogami to create Remocon and Engine Bros, which would be used by soldiers of Seito, Nanba's prefered choice to inherit Japan. Utsumi was given the personal thanks of Seito's Prime Minister Masakuni Mido.

Personality
Nothing is much known about Utsumi's personality other than being a loyal assistant to Gentoku, even when his superior is revealed to be the leader of Faust and manipulating the Touto government from behind the scenes, as shown smirking whenever Gentoku, as Night Rogue fighting Blood Stalk. Though, he does seem slightly hesitant and reluctant at times as well.

It is later revealed that there is also a hidden depth to his personality, as Utsumi admits to Sento that they have a lot in common whenever they are trapped in unfitting situations they are in. He wanted to live a simple life as a scientist, though he admitted that he had lost his way as time passed, and warned Sento not to fall down the same path as him as a fellow scientist.

After being saved by Stalk and working with Nanba, Utsumi seems to be more open-minded. He also faintly smiles after he finished the battle simulation with Sento. Ha demostrado un lado maniático y despediado cuanto hizo a rodillarse y pisando la mano de Gentoku Himuro.

Powers and Abilities

 * High Hazard Level: It is implied that Nariaki seems to have a high Hazard Level, due to his capability of using the Transteam Gun.
 * Genius-Level Intellect: Since Utsumi had worked for the Touto Institute, he possessed a certain level of intellect and this allows him to elevate to the rank of Gentoku's assistant. Because of this, Gentoku had speculated that Utsumi had a hand in the creation of Hokuto's Sclash Driver for Kamen Rider Grease, something which Sento Kiryu also suspected; this is later confirmed after Seito invades Hokuto, when it is revealed that Utsumi has built and upgraded another Sclash Driver for use by Kamen Rider Rogue, as well as duplicating Kaisei Mogami's Nebula Steam Gun for use by the Hell Bros, all as part of Nanba Heavy Industry's partnership with Seito.

Forms
"Bat! Mistmatch! Bat...Ba-Bat... Fire!"

- Transformation announcement

Ability Perimeters: Like Blood Stalk, Night Rogue's form is accessed with the Transteam Gun and the Bat Fullbottle.
 * Height: 197.5 cm.
 * Weight: 103.0 kg.
 * Punching power: 17.2 t.
 * Kicking power: 20.5 t.
 * Maximum jump height: 49.0 m.
 * Maximum running speed: 100 m. per 4.1 sec.

Unlike Build, Night Rogue's Ability Perimeters are not spread out between his arms and legs. While Night Rogue gets power from only one Fullbottle, he's much stronger than Build's Trial Forms and his stats even surpass some of Build's Best Matches.

Utsumi's transformation into Night Rogue allows him to last for a good while against Build's Hazard Forms, at most before Build starts losing control. Utsumi, as Night Rogue, can also use his visor to analyze Build's stats.

Appearances: Build Episode 12, Raising the Hazard Level ~7 Best Matches~: First Chapter

Devices

 * Transteam Gun - Transformation device and personal weapon.
 * Fullbottles - Transformation trinkets.

Weapons

 * Steam Blade - Standard sidearm weapon. Can combine with the Transteam Gun to form the Steam Rifle.

Other

 * Tablet - While working under Faust, an by extension Nanba, Utsumi is in possession of a tablet that allows him to create holographic Smash. The Smash holograms created by this device emit electric pulses upon contact, making them more realistic, hence they are suited for combat simulations.

Portrayal
Nariaki Utsumi is portrayed by Yuki Ochi (越智友己). His suit actor as Night Rogue is Jun Watanabe (渡辺淳).