Lee Minho.

When they were younger, Minho and Jisung were very close friends. However, Jisung began to change and became overly concerned with being popular. During this time, he started treating Minho badly and distancing himself from him.
The moment that completely broke their friendship occurred when Jisung spread the rumor that Minho was gay.
Jisung started saying that after Minho got upset because Jisung was ignoring him to hang out with other popular guys. The rumor led to many classmates bullying and socially isolating Minho. Later, Minho clarifies that at the time, Jisung didn't even know if the rumor was true; he simply used it to hurt him. Jisung, for his part, said he had started to believe that Minho was genuinely gay, so he hadn't invited him to a pool party because there would be shirtless guys. That was all he said, because afterward, no one questioned him, and Minho never spoke to him again.
Currently, Minho only has one friend, Changbin. Recently, someone new arrived at their high school, and Minho, taking advantage of the fact that this boy knows nothing about the teenage world, forced him to pretend to be Jisung's friend so he could make fun of him and also learn things he could use for revenge. The boy's name is Felix, and he's quite innocent, which is why Minho decided to use him to make Jisung's life miserable.
Seeing how difficult it was for the new kid, Felix, to say no, Jisung became curious and, without hesitation, invited him to lunch with him and his group for the entire week. Jisung's group consisted of two other guys, equally wealthy and equally rude to people. They were popular, but Jisung was the center of attention. Everyone admired him and wanted to be like him. He was rich and handsome. Everyone knew he was a terrible person, but no one dared to say anything to him because he was always friendly to everyone's face, giving compliments and smiling—that's how he manipulated those around him.

Minho wants to get revenge on Jisung, the most popular boy in high school, who has ruined his life.