Vampire Woo-hyeol has one desperate wish: to become human and experience heart-pounding love. He tried many ways to become human, but none of them worked. After hearing from a 1000-year-old cat that he can become human if he sleeps in a hawthorn coffin for 100 years, he enters the coffin for a lengthy slumber.

With only one day left in his 100-year goal, he fails to become a human being. He is even bitten by a woman, In-hae, causing him to faint. Yang-nam advises him to keep her by his side and watch her over, as she doesn't seem to be an ordinary person. Meanwhile, In-hae encounters a real estate scammer and gets involved in a chase to catch the fraudster, but finds herself in danger...

In-hae finds out that Woo-hyeol is a real vampire. However, what Woo-hyeol buys with her credit cards even makes her more shocked. She threatens to sell the mansion if Woo-hyeol can't repay his debt and starts living with him under a contract. Woo-hyeol reunites with two vampires named Sang-hae and Dong-seop in the second-hand market. They lament the world in which vampires are drained by humans.

The blood on In-hae's lip triggers a memory in Woo-hyeol, reminding him of Hae-sun. Woo-hyul wonders if In-hae is the reincarnation of Hae-sun. In-hae is concerned about her first kiss with Woo-hyeol and feels more uncomfortable seeing him, who is employed as a janitor at the school she works at. Yang-nam tells Woo-hyeol that if he drinks In-hae's blood, filled with love, he can become human.

Woo-hyeol strives to turn In-hae's blood into full-of-love, but she shows no interest whatsoever. To make matters worse, rumors spread within the school that Woo-hyeol and In-hae are dating, which resulted in In-hae losing her job. Feeling upset, In-hae drinks heavily and confides her past to Woo-hyeol, and his genuine reaction makes her heart pound.

In-hae struggles to find a new job. Do-sik suggests In-hae start a guesthouse using her mansion. Although Woo-hyeol strongly opposes the idea at first, he eventually agrees because there is no other way for In-hae and Do-sik to become closer. As Woo-hyeol realizes Do-sik's affection for In-hae, he feels a pang of jealousy. Meanwhile, someone whom Woo-hyeol has longed for appears before him.

Woo-hyeol is surprised to see Hae-won, who looks exactly like his past love, Hae-seon. He can't approach Hae-won because she doesn't seem to remember her past life. As In-hae feels sorry for Woo-hyeol, she invites Hae-won to a dinner for Woo-hyeol to spend some time with her. However, In-hae becomes anxious, thinking that Woo-hyeol's vampire identity might be revealed during dinner.

Woo-hyeol and In-hae are forced to leave the mansion due to construction. Now that they are apart, they strangely think of each other more. However, Woo-hyeol starts experiencing physical symptoms and hears from Yang-nam that if he doesn't consume In-hae's blood, filled with love, he will die from it soon.

Do-sik discovers that Woo-hyeol is a vampire and tests In-hae, who unexpectedly protects Woo-hyeol. Woo-hyeol, troubled by the fact that he needs In-hae's blood to survive, faces additional challenges when Hae-won becomes more affectionate towards him. Desperate to obtain In-hae's blood filled with love, Woo-hyeol's heart is tormented.

In-hae cannot understand Woo-hyeol, who says he needs to have her blood filled with love. Woo-hyeol proposes a deal where, if In-hae provided him with her blood, he would leave the house. Meanwhile, Hae-won asks In-hae to throw a party to get closer to Woo-hyeol. Everything seems to go smoothly, but In-hae cannot shake off a sense of unease.

Woo-hyeol and In-hae develop strange feelings towards each other after the party. Do-sik, who realizes something is going on between them, tries to take them apart by letting In-hae know that Woo-hyeol is a vampire. However, In-hae takes Woo-hyeol’s side instead. In a drunken state, Hae-won calls Woo-hyeol, and while he's on his way to drop her off, he discovers a shocking truth.

While nursing Woo-hyeol, In-hae and Woo-hyeol confirm their feelings for each other. At Gwang-ok's request, they spend time together while taking care of Min-jae. Meanwhile, Do-sik, who is holding hands with Man-hwi, begins to suspect Woo-hyeol of being a half-vampire. Upon realizing that Woo-hyeol is aiming for In-hae's blood to become human, Do-sik immediately sets out to chase after Woo-hyeol.

In-hae's long-awaited father makes a return, but her emotional wounds make it difficult for her to accept him. Meanwhile, Woo-hyeol's health continues to deteriorate, deeply saddening Sang-hae and Dong-seop as they realize that time is running out for him. Meanwhile, as Man-hwi fails to capture Woo-hyeol, Do-sik takes matters into his own hands.

In Hae's long-awaited father makes a return, but her emotional wounds make it difficult for her to accept him. Meanwhile, Woo Hyeol's health continues to deteriorate, deeply saddening Sang Hae and Dong Seop as they realize that time is running out for him. Meanwhile, as Man Hwi fails to capture Woo Hyeol, Do Sik takes matters into his own hands.

As Woo-hyeol accepts the fact that there's not much time left for him, he decides to spend the remaining time with In-hae. Do-sik, upon finding out that Woo-hyeol is getting close to death, also becomes anxious. Will Woo-hyeol and In-hae be able to hold onto their love until the end?