Yasuo is a student in Kasugayama High School; he had many ideas on how the school should be run and how power should be administered; namely, he wanted to empower himself. However, his few social graces did not endear him to his peers and left him without any possibility to realize his dreams of power until he called the Joker to make him student council president.
In exchange for his services, Joker demanded he scatter the rumors about the cursed emblems of Seven Sisters High School, promising to make him an Executive of the Masked Circle. Yasuo, desperate to consolidate his power, also spread rumors of the strength of Hiroki Sugimoto (one of his few allies) and how he was stronger than "Death Boss" - Eikichi Mishina's favored alias. Unfortunately, Eikichi still defeats Sugimoto because Yasuo didn't refer to Eikichi by name in the rumor, but only by his title, allowing Eikichi to rescind his title and circumvent the rumor.
At the time of the humiliating defeat of Sugimoto at Club Zodiac, Yasuo was organizing the Cuss High school festival, which he was to use as an opportunity to gather Ideal Energy from the assistants to the school's dance. During this, rather than directly engage Tatsuya Suou's group, he lured them into the school's fabled bomb shelter in the hope they would die there (though he did offer Maya Amano the possibility to escape, she gleefully spat it back to him).
During the dance the next day, Yasuo used the crystal skull he had been provided with to drain the energies. However, he did not consider the possibility of the group finding the bomb shelter's legendary exit, and was left to escape cowardly as he was confronted. Trapped in the roof of Cuss High, Yasuo was forced to defend himself. He was defeated and left to stew in his defeat.
At that moment, two other Masked Executives teleported in - King Leo and Lady Scorpio. Decrying him as a failure to the Circle, King Leo immolated Yasuo.
At the end of Innocent Sin, he was resurrected and placed in the new timeline with no memories of his time as a potential Executive. He was later seen in Eternal Punishment as the hopeless, useless candidate he truly was. Yasuo can be found on the roof of Kasuyagama, explaining his ideals to another student and will not acknowledge Maya and the others.