Kurosaki, Tasuku

黒崎祐

Kurosaki works as the school janitor. He is also a computer hacker.
He is a drinker, smokes heavily, is violent, dangerous, and scary, and calls Teru his servant. He is quite good-looking as well. He does not display his emotions normally, but when he gets angry, he can be very terrifying. He swears at times and likes to eat. He is an excellent cook, but usually commands Teru to cook. However, he can be protective of Teru when she is in danger. And yes, he is in love with her.

Spoiler

His father was once part of a research development team for a code system called Jack. His father supposedly betrayed the team and suddenly died, leaving Tasuku alone. To investigate the truth behind his father's death, Tasuku became a hacker, and during the process, invented a code virus named Jack O' Frost, a virus that changes every data inside the infected computer to turn into a code. It's a really dangerous virus, and since he was the one who made it, he was a wanted man by the government.
Soon after, Tasuku entered the company at which Kurebayashi Souichirou was working. Even though everybody else treated Tasuku differently because of his status as a genius hacker and son of a supposedly traitor, only Souichirou truly believed in Tasuku's father's innocence and thus, defending Tasuku. Souichirou even promised to protect Tasuku, as his 'oniichan'. Tasuku gradually became fonder and fonder of Souichirou, and even thought of him as his own older bro.
But the peace didn't last long. The bad guys asked Tasuku to meet up with them and pressured Tasuku into remembering his own past sin, the Jack O' Frost, maneuvered him into spreading it to the whole computer in the company he was working at, by making use of Tasuku's guilty conscience and Tasuku's wish to be forgiven. They used Professor Midorikawa's death to shake up Tasuku's mental and made him think that Midorikawa's death was caused by his Jack O' Frost. Thus, Tasuku spread the virus and disappeared.
Meanwhile, the police officers met up with Souichirou, who already had a stomach cancer at that time, to help decipher the codes Jack O' Frost had made, even though the code was extremely difficult, to find the evidence regarding Midorikawa's death. Although Souichirou should not overexert himself, he still did it anyway, because at that time Tasuku was accused of killing Midorikawa, and the evidence inside the computer was the only thing to prove his innocence.
Souichirou didn't want to give up on Tasuku, he still believed in Tasuku and he continued to pursue him. Souichirou managed to arrive on time and prevented Tasuku from committing suicide.
Everything might seem like it has gotten back to normal, but soon after that, Souichirou died because of his cancer. Upon his death, he entrusted his younger sister, Teru, to Tasuku's care.