Ryushi Korogane

(koro sensei human version i found his real name) Korogane loved sweets almost to extreme cases, and was also shown to be a very perverted character, This characteristic was revealed to be the side effect of the experimentation which made him unable to hide his true feelings. Korogane was born in the slums of an unknown third world country, where he soon learned he had a natural talent for killing and never bothered using his empathy. He became an assassin, murdering anyone for the right price, even world leaders and the heads of entire militaries. he's an experiment when he was human, right?