Calvin Larsen seems like a carefree rich playboy, but he is secretly the strongest fighter alive. The Rejuvenation Elixir he created on a whim draws the Larsen family into danger. Unaware of the truth, his parents hire the feared Executioner, Claire Grant, as his bodyguard, not knowing she is actually his long-lost fellow disciple. As threats escalate, Claire faces enemies head-on while Calvin eliminates the real dangers from the shadows. When everything is at stake, he finally reveals his true power, and their relationship evolves from employer and bodyguard into a bond of love and devotion.
