Afraid of losing Yeo Wool, Kang Chi breaks up with her. She holds onto him, saying that losing him is what she fears most. Upset by the breakup, Yeo Wool goes out to clear her head and is attacked by a mysterious figure.
Kang Chi visits Monk So Jung, saying he wants to find the Gu Family Book so he can grow old with Yeo Wool. So Jung reveals their fate: one of them must die. Kang Chi is shocked. Meanwhile, Tae Seo is captured and taken to Jo Gwan Woong.
To find the suddenly vanished Yeo Wool, Kang Chi seeks out Wol Ryung in the forest. Kang Chi begins to fight Wol Ryung to save her. Meanwhile, Ja Hong Myung meets with Jo Gwan Woong, stating she wishes to buy one of his properties.
Gu Wol Ryung appears at the school and tells Kang Chi to give up on becoming human. After Wol Ryung attacks and vanishes, the school members mistake him for Kang Chi. Meanwhile, Ja Hong Myung summons Tae Seo and asks if he is one of Jo Gwan Woong's men.
Yeo Wool encounters Gu Wol Ryung in the forest and is terrified. Wol Ryung tells her that Dam Pyung Joon is the one who killed Kang Chi's father. Rumors spread that Kang Chi is the son of a gumiho. Jo Gwan Woong declares that Kang Chi is responsible for the murders in the forest.
Kang Chi and Yeo Wool enjoy the lantern festival. However, when a disciple is found dead with his liver eaten, Kang Chi falls under deeper suspicion. Tae Seo returns to the inn and tells Jo Gwan Woong about Yi Sun Shin's plan to build a new 'ironclad' ship.
Yeo Wool is put in charge of Kang Chi's discipline at the school. Despite their bickering, they grow closer and go to see the lantern festival. Meanwhile, unusual corpses are found in the forest, and the school's disciples begin to suspect Kang Chi.
To save Chung Jo, Tae Seo reveals Kang Chi's location to Jo Gwan Woong. Tae Seo attempts to behead Kang Chi himself and cuts off his prayer bead bracelet. Kang Chi transforms into his beast form in front of Tae Seo and Chung Jo. Seo-bwagwan, sensing Kang Chi is Wol Ryung and Seo Hwa's son, reports this to Jo Gwan Woong.
Enraged by Jo Gwan Woong's atrocities, Kang Chi's eyes turn red, and he lunges at him. Jo Gwan Woong frames Park Mu Sol for high treason and Kang Chi for murder.
Kang Chi and Yeo Wool are attacked by dark shadows. Kang Chi, unfamiliar with such opponents, is cut multiple times while fighting back. Hearing Kang Chi is injured, Chung Jo visits him out of worry, and they share an affectionate hug. Yeo Wool witnesses their embrace.
Jo Gwan Woong visits the Hundred Year Inn. Tae Seo politely informs him there are no empty rooms, but Gwan Woong becomes enraged and causes a scene. Kang Chi, who had been kicked out by Lady Yoon, hears the news and, after some conflict, returns to confront Jo Gwan Woong.
Following Buddhist Monk So Jung's advice, Park Mu Sol adopts and raises Kang Chi. Afterward, he succeeds in all his endeavors, building the Hundred Year Inn, the best in the south. Now an adult, Kang Chi causes trouble while trying to stop the marriage of his first love, Chung Jo.
Having given his heart to Seo Hwa, Gu Wol Ryung wishes to give up his immortal life to become human. He seeks to obtain the Gu Family Book by observing three taboos. Wol Ryung and Seo Hwa hold their own wedding and spend happy days in the Moonlight Garden, but Jo Gwan Woong remains relentless in his search for the missing Seo Hwa.
In the Moonlight Garden, rumored to be home to ancient mountain spirits, the guardian god of Jiri Mountain, Gu Wol Ryung, roams the human world. When Yoon Cham-pan is falsely accused of treason and executed, his daughter, Seo Hwa, is sold off as a gisaeng.
Park Soo Jong leads his troops to the palace, declaring he will take over as regent to fix the state's affairs. Meanwhile, Sadam is enraged to find that Do Ha, who was trapped inside a painting, has disappeared.
Kisan is shocked to hear ghosts are killing palace staff Lee Rin and Do Ha vow to stop them. Do Ha sees her sister Yeon Ha's face superimposed on Mo Yeon Wol, preventing her from being harmed.
Jo Sang Heon cannot distinguish the real Do Ha from the fake one, as both bear the Night Watchman's mark and the magic reveals no ghostly energy. Meanwhile, Kisan orders tax hikes and more manpower to speed up the pagoda's construction.
With Do Ha's help, Lee Rin breaks free from the ghostly energy. However, he pretends to still be possessed as part of a plan to trick Sadam. Maeng Sa Gong joins the Night Watchmen to help defeat the Eokgwi.
A malevolent ghost (Eokgwi) stares down at the sleeping Lee Rin and blows dark ghostly energy into his ear. Meanwhile, Kisan appoints Lee Rin as the head of the Changcheon Pagoda's construction.
Enraged, Lee Rin tries to show Park Soo Jong his mother's blood-written letter, but Rang stops him. Soo Ryun tells her father that his power is the only way for her to have Lee Rin, insisting he must not lose.