Season 2

Summary

While Zenny was still on his throne, the hostile relationship between humans and monsters had worsened. He tried his best to solve it, but none of his plan worked. After his death, the whole world erupted into wars between humans and monsters, and both of them hated each other more.

At the same time, Frisk and Jack just got married. Frisk told Jack that she wanted to visit her step-father, Sans, who gave her the knife. Jack felt that Sans was a bit suspicious about the knife, but he went to visit him with Frisk anyway. During their visit, Sans told Frisk his ultimate plan: Kill the entire human race to facilitate peace within the monsters' community. He told her that he gave her the knife because he knows that it can control her to make her go genocidal and therefore he could use her as a tool to kill humans.

That night, he brainwashed her. And with that, Frisk started her mission of killing. She killed Papyrus, who tried to stop her. Jack got to know what happened to Frisk, and when Frisk met him, all she knew...was kill.

Knowing who she was, Jack fought her with mercy. He even tried to recall all of her lovely memories with him using his magic. Frisk gradually lost her genocidal infection and recognized Jack. Upon recalling her memories for the fourth time, she couldn't help but kneeled to the ground and burst into tears.

"Jack...I...I know I don't deserve this...but I really want to feel your warming soul...your hug...I don't deserve it. Please...kill me. I don't deserve a life in this world."

Hearing this, Jack hugged her. "Silly girl...you deserve all of this, because I love you. Who says that love is conditional? I can always love your soul, I can always hug your soul, I can always warm your soul." And with that, the two lovebirds got reunited.

A few weeks later, Sans's plan got exposed to the public and he was executed with immediate effect. Meanwhile, Jack solved part of the monster-human conflict by signing a number of peace treaties with the monsters. Eventually, he became the king of the underground, while Frisk got onto the queen's throne.