Keima explains to the audience how he has captured fourteen girls and two unique girls after the last season. Meanwhile, Kanon is preparing for her school tests, but ends up talking with her split personality, Apollo, who claims to be a goddess. The next day, Keima and Elsie meet up with Tenri and within her, Diana. Diana wants Keima to marry Tenri as Tenri's love for Keima increases her powers, which he refuses. When asked to explain what she is, Diana reveals she is a goddess, one of the Jupiter Sisters, who helped the New Demons of Hell against the Weiss, when they attempted to take over the three realms of Earth, Heaven and Hell, and control all souls. After defeating them, the Jupiter Sisters sacrificed themselves by sealing themselves together with the Weiss, but they escaped ten years ago. Diana asks Keima to help find her sisters and reveals they reside in his past conquests, who did not forget their memories with him.

Apollo casts a warning in the sky to her sisters to trust no one before succumbing to her wounds. Lune attempts to finish her but is stopped by Nikaidō. Keima, Diana, Elsie and Haqua have Apollo taken to the Katsuragi household where they discover the magic dagger used on Apollo and Kanon is ancient Weiss magic and the culprits are Vintage, a group of demons who wish to resurrect the Weiss. With Kanon having a week to live, Keima must find the other four goddesses to heal her before Vintage gets them. To accomplish this without incident, Elsie disguises herself as Kanon and Keima tricks his mother to go to South America. Partnering with Haqua who is disguised as Elsie, Keima uses the rumor of Kanon's confession to see the reactions of his prior conquests, who will act jealous if they remember falling in love with him. Keima narrows his suspects to Ayumi, Chihiro, Shiori and Tsukiyo Kujyo, who were all embarrassed around him.

Keima plans to spend an hour each with the girls to raise their affection for him without any of them encountering each other with Haqua's help. He manages to succeed with Tsukiyo on the bus but compilations occur when the 2B-Pencils finish band practice early which leaves Haqua with Chihiro. As a result, he misses Yui but continues by walking home with Ayumi and Miyako. Unfortunately, Haqua and Chihiro are heading in the same direction which prompts him to take Ayumi and Miyako inside the mall. After making sure Chihiro is busy with Haqua, he has a private talk with Ayumi that he won't give up on her. Next, he meets up with Chihiro at the music store where he praises a song she wrote. Later, he heads towards the library to meet with Shiori where he finds a story written about them that resembles her conquest with the roles reversed but his character is killed due to the rumors with Kanon.

Keima arrives at the library whereupon Shiori allows him to read her story while being watched. Meanwhile, Nora discovers Kanon and demands Haqua an explanation. In the library Keima discovers that Luna, Tsukiyo's doll, is Vulcanus who warns Keima never to approach Tsukiyo again. Attempting to stop Vulcanus from being discovered, he approaches Tsukiyo not realizing she is in fact truly Vulcanus controlling objects. With both Vulcanus and Tsukiyo mad at Keima for cheating on her, he makes Tsukiyo remember the promise he made to her. Succumbing to her pity for his injury, Tsukiyo kisses Keima whereupon she grows wings. Nora explains to Haqua that Vintage have infiltrated the spirit hunters and the search order for the goddesses is a plot to capture them. Reunited, Diana and Vulcanus combined their powers to removes the cursed dagger but Apollo turns Kanon's body into a liquid state as a preservation measure.

Keima sends Tsukiyo home warning Vulcanus not to reveal herself while he searches for the other goddesses. Unexpectedly, Yui has come to Keima's home to ask him out. Keima explains to Haqua he must now conquer Yui before Vintage realizes she has a goddess. The next day, Keima crossdress as a girl which gains Yui interest to awaken her past memories while unknowingly being overseen by Shiori. After Keima asks her out for a date, the goddess Mars finally awakens inside of Yui. As the crossdressing couple spend time together on their date at an amusement park, Keima is kidnapped by a Vintage agent. Wishing to save Keima, Yui's love for him finally restores Mars' powers which she defeats the agent who is revealed to be Haqua which was a part of Keima's plan to awaken her powers. Yui proclaims her love for Keima and kisses him, which restore Mars' wings.

Shiori is having trouble finishing her novel for the Mai High Festival due to her conflicting feelings for Keima. She then notices a young girl, who is actually her goddess, and chases after only to meet up with a crossdressing Keima. As she inquires his crossdressing and eat at a Ramen shop, Shiori tells Keima that she wants to make a story of him. Keima explains to Haqua that with Shiori's boosted confidence after their talk, she can now finish writing her novel. But the next day, Shiori is suffering writer's block so Keima decides to stay with her at the library to help her. After several drafts and procrastination by reading books, Keima eventually tells Shiori to write about herself especially when they both lock themselves in the library. Realizing Keima was there and kissed her during that time, Shiori starts writing. The next morning, Keima reads her story about her life at the library which ends with her declaring she loves Keima.

Keima gets sick from a cold so Nora's partner Ryo is ordered to watch over him. With two targets left, Keima decides to use his cold to get Ayumi to visit him by calling her while he calls Chihiro not to come so both of them won't visit at the same time. At his home, Ayumi decides to stay to take care of Keima after seeing him sick. Just when things were going according to his plan, Chihiro unexpectedly visits no thanks to Ryo letting her in. With no choice, Keima hides Ayumi under his bed as Chihiro takes care of him while trying to simultaneously raise both girls affection. After Chihiro leaves the bedroom after singing her song for him, Keima tries to explain to an angry Ayumi nothing is going on between him and Chihiro. But Chihiro knocks on the door and confesses to Keima which he feigns ignorance before she leaves. Keima tries to call Chihiro but Ayumi contacts her first where she admits she heard Chihiro's confession and supports her.

While attending a meeting between the section chiefs in New Hell, Haqua questions Dokuro Skull if Vintage have infiltrated the spirit hunters which the latter denies. However, Haqua is arrested by Public Safety which she later learns to her shock from Nora that Vintage have also infiltrated the highers ups and Dokuro Skull was the one who ordered her arrest. Back at Earth, Keima gathers all the awakened goddesses at his house in order to undo the spell casted on Kanon and awaken Apollo. During the ritual, Keima is brought to Apollo's realm. There, Apollo reveals she cannot leave now as she stopping the power of the Weiss from spreading the city but can only do so for three more days. Kanon and Apollo put their faith on him and grow their wings before he returns back home. While Majima High prepares for their upcoming festival, Ayumi becomes a participant of a pageant as Chihiro invites Keima on a date.

Chihiro and Keima head to the rooftop to continue their date. As they are about to kiss, Chihiro asks him to be gentle as this is her first time, which leads Keima to realize that Chihiro doesn't have a goddess as she does not remember her first kiss with him.

Ayumi is still angry with Keima but is forced to work with him after he becomes the 2-B Class Cafe barista. Keima tries to talk with Ayumi but her anger and Chihiro being there doesn't help. Meanwhile, Lune orders Vintage to target all of Keima's past conquests.

As Ayumi contemplates on what Keima said to her, Keima ask her to meet him at Kozue River. Haqua explains to Chihiro why Keima has to make Ayumi fall in love with him as he tries to make her like him again. However, their date is constantly interrupted by Vintage which Chihiro suggests she, Keima and Ayumi stay at Miyako's home.

As they head to Ayumi's location, Chihiro tells Keima he should tell the truth to Ayumi as unknown to Keima, she already told Ayumi that he was trying to win her heart for something important. At the harbor, Keima tell Ayumi he will honestly tell the truth if she ask anything before continuing their wedding.