Shōsaku Katsura

Shōsaku Katsura (桂 正作,) is the bomber who harbors a grudge against Kunikida's ideal.

Appearance
Katsura is a young man, likely in his late teens. His hair is black and hangs in front of his eyes. He wears a black turtleneck shirt, dark grey pants, black gloves, and dark shoes. Over his clothes, he wears a black coat with a hood. In the past, he appears to have worn a gakuran school uniform.

Personality
Katsura appears to be wholly focused on what Kunikida told him two years ago, to the point of almost being obsessed. He is intelligent, having planned ahead with regard to the bombs and their setup. His desire to destroy Kunikida is not driven by revenge, but his desire to get rid of Kunikida's ideal, as well as test it. He seems to consider himself weak, and much of his actions seem to indicate an inability to accept himself.

When Kunikida chooses to blow himself up with Aya, Katsura appears to look upset as his "testing" of Kunikida's ideals did not work out the way he had hoped. Kunikida tells him again, that he won't let anyone die in front of him, and when Katsura is being arrested, he smiles, perhaps accepting Kunikida's ideals and beliefs.

Later when speaking to Fyodor, Katsura seems to have changed, having great respect for Kunikida, subtly defending him and saying that Kunikida's ideals are the real thing.

Background
Two years ago, he was arrested by Kunikida after planning to detonate an explosive in his school. Kunikida spoke to him, telling him to "live on with courage" and those ideals stuck with Katsura. Katsura found those words condescending and planned for two years to beat Kunikida in order to erase the words Kunikida had said.

The Guild Aftermath Arc
Katsura delivers a suitcase with an explosive in it to Aya before running away. When Kunikida and Aya go to search for him, they notice that bombs have been placed on the train tracks. Taking advantage of a distracted Kunikida, Katsura manages to strap a bomb to Aya. He uses this as a way to disarm and tie up Kunikida. Katsura beats Kunikida with a stick, angry about Kunikida's ideals that have haunted him. Kunikida manages to trick Katsura into opening his notebook, and releases a stun grenade. Using the distraction, he breaks free and ties up Katsura.

Despite being tied up, Katsura presents Kunikida with an ultimatum: choose between disarming the bombs placed on the train tracks, or disarm the bomb attached to Aya. After Kunikida chooses to blow himself up with Aya, Katsura is shocked. When Kunikida and Aya are revealed to be safe through Yosano's ability, Katsura is taken into custody by the police.

Cannibalism Arc
During the events of Cannibalism, Fyodor kidnaps Katsura and plays cello to him, to which he humors Fyodor if he merely brought him there to listen to his playing. Fyodor answers that he only wishes to know what transpired between him and the Agency, wondering if Kunikida's bravery is tantamount to saving a single girl from an explosion. Katsura yells that Kunikida's ideals are the real thing and that Kunikida's spirit cannot easily be broken, to which Fyodor responds with a mere smirk.

Quotes

 * (To Doppo Kunikida) ""I refuse to let anyone die before my eyes." That was y our ideal, right? So kill that girl and prove it to me... prove that your ideals are a pipe dream! That you're just as human as I am!"
 * (To Fyodor Dostoevsky about Doppo Kunikida) "His ideals are the real thing! There's not a soul out there who can break his spirit!"

Trivia

 * Katsura is named after the main character of real-life 's work An Uncommon Common Man (非凡なる凡人,).