|Novel Debut:||Last Girl Standing|
|Anime Debut:||Episode 3|
Sonic Boom (ソニックブーム, Sonikku Būmu) is a Soukaiya Six Gates ninja. He has been known to go under the name Fumatoni (フマトニ, Fumatoni). It is unknown if this name is a pseudonym or his real name.
Part 1: Neo-Saitama in Flames Edit
Last Girl Standing Edit
He bails out Shogo and makes him join the Soukaiya and renames him Suicide. He then orders Suicide to kill Yamoto Koki, Suicide's classmate and girl he landed on when he attempted to kill himself. Suicide attempted to fight him off to let Yamoto and her friends escape but he proved to be much stronger than him. Yamoto then tried to fight him but was not strong enough as well, however, Ninja Slayer was there to save Yamoto and they teamed up and killed Sonic Boom.