Eiichirō Saiyama

Eiichiro Sayama is an antagonist featured in Danganronpa Gaiden: Killer Killer, a spinoff manga for the upcoming Danganronpa 3: The End of Hope's Peak Academy.

Eiichiro is a serial killer who has been murdering people since his debut as a mangaka. He was murdered after his crime was found by Takumi Hijirihara, the Killer Killer in chapter 3.

Prior to the Tragedy
Eiichiro wanted to become mangaka since he was in elementary school. A girl from his class praised his drawing and wonder if he wanted to become a mangaka in future. Eiichiro overjoyed because that's the first time that someone compliment him. Ironically, until he became a success mangaka in his 32, no one praised him ever again.

Chapter 3 - Bessatsu Shounen Zetsubou Magazine
Eiichiro was a success mangaka that wrote a documentary serial manga series. The tragedy that he drew was none other than The Biggest, Most Awful, Most Tragic Event in Human History.

One day, Takumi, a member of SCI and also a fan of Eiichiro's work came out from a delivery box and without permission entered his apartment. Inside, Takumi revealed that Eiichiro's corpse depictions were too realistic. Takumi revealed inside that Eiichiro has been killing people and kept their corpse inside his "assistant" room that he used as inspiration to drew corpse depictions.

Eiichiro angered at Takumi who once again, a reader who won't praised his work. Before Eiichiro could killed him, Takumi performed a copycat murder. Eiichiro was impaled by his own giant pen by Takumi, copying the death of a victim of the High School Killing Game, Mukuro Ikusaba.

Trivia

 * One of Eiichiro's victim crucified with ropes to two poles similarly as Chihiro Fujisaki's body being crucified in the Killing Game of Class 78th.