Sento Kiryu/Kamen Rider Build

Sento Kiryu (桐生 戦兎 Kiryū Sento) is a genius theoretical physicist who experiments with Fullbottles to further enhance his abilities as Kamen Rider Build (仮面ライダービルド Kamen Raidā Birudo) to fight against the evil Smash organisms. He is a man with no memory of his past, and fights to find the truth about himself. Initially believed to be someone named Taro Satou (佐藤 太郎 Satō Tarō), his true identity turned out to be someone else.

Description
Sento's outstanding traits are his intellect, narcissism, and sense of justice. A genius by all standards, Sento has repeatedly displayed advanced knowledge in physics, mathematics, chemistry, engineering, and cryptography.

Sento's polymathism is accompanied by an inflated ego and sharp tongue: he likes to praise himself for his works, and often mocks Ryuga for his comparatively lower intelligence. Sento often relies on his own skills to solve problems and never expects sudden assistance from others, so when it happens, he tends to either be surprised or turns them down. Also, Sento can be easily caught off guard when he accomplishes anything or witnesses something unexpected and new which excites him, because of his reliance on his intellect. In this state, he is vulnerable to any surprise attacks.

Sento can be easily attracted to anything that is mysterious and interesting, such as new innovations and anything that brings him closer to uncovering his past, and will relentlessly pursue it. This will continue until either he reaches a conclusion or someone forcibly stops him during progress. When Sento gets excited (usually due to a discovery or breakthrough), a part of his hair sticks up.

Sento's greatest trait is his sense of justice. A firm pacifist, he believes that science should be used for the sake of humanity, and harshly opposes using it for war. His selflessness and sense of duty causes him to try and shoulder the burden alone rather than involve others, whether he can carry that burden or not. This altruism intensifies the guilt he feels for his role in creating the Smash and escalating the war. While generally calm and composed, Sento is prone to making poor judgement during emotional turmoil.