The cast members are introduced through an interview with 3 variety show masters from 1 Night 2 Days, and meets each other for the first time. Kim Sook is chosen as the first dreamer, and her dream is to be a tour bus driver. The members divide into two teams, one to get the license (Kim Sook, Jessi, Tiffany) and the other one to find a mentor for learning to drive (Ra Mi-ran, Hong Jin-kyung, Min Hyo-rin).

Both teams proceed with their assigned task, and Jo Se-ho comes to inform them about road safety.

The members go to MT as proposed by Kim Sook, and chooses the second dreamer. During the trip, the members are fulfilling their wishes as well as the rule. Min Hyo-rin is the first to get her wish, which is to do a makeover for the older sisters. Kim Sook gets her wish to eat alone, and Tiffany gets her wish to visit an amusement park.

The sisters arrive at the dorm and spends the night playing games getting to know each other. The following morning, Jessi gets her wish to try bungee jumping.

Min Hyo-rin is chosen as the second dreamer. Her dream is to debut as a girl group member and they get help from JYP as the producer.

The members visit KBS Music Bank and have battle with TWICE members through games. They also hear the completed song for their debut, "Shut Up". Afterwards they visits I.O.I and have talks regarding debuting as girl group from different agencies.

Kim Sook & Jessi are taking the exam for the bus driver's license. The sisters also work on the second dream and get their girl group name.

JYP teaches the girls the choreography for their debut song. They also get their personality checked through MBTI test, and celebrate Tiffany's solo (I Just Wanna Dance) at KBS Music Bank.

With Tiffany missing through a concert schedule with Girls' Generation, the rest of the girls work on the singing and choreography for their song. Ra Mi-ran and Kim Sook consult with Jo Kwon and Yenny. Min Hyo-rin and Hong Jin-kyung consult with Kim Tae-woo, while Jessi is working on the rap.

The first recording for the song, and more work on the choreography. The members also decides on the costumes and makeup style.

The recording continues for the chorus and rap part, but Hong Jin-kyung still struggling with her part which makes her stays longer at the studio while the other members perfect the choreography. After the recording, Min Hyo-rin invites the members to her house.

As debut date is getting near, the members work harder on the choreography. Later Bada & Shoo from S.E.S visit them to give tips on debuting as girl group.

The shooting of "Shut Up" music video with guest starring Kim Joon-ho as Min Hyo-rin's boyfriend and Yoo Hee-yeol as Min Hyo-rin's previous boyfriend.

The shooting continues with several cameos appearance.

The sisters go for a trip to relax and open up to each other.

The Unnies finally debut live at Music Bank (while still maintaining their #1 rank at online music charts). The second dream comes to an end and the members present a gift to Park Jin-young as they bid farewell.

Jessi is chosen as the third dreamer, choosing to learn boxing. But after starting this dream, she discovers that the other members' prepared a surprise with the crew: her real dream is to spend time with her parents who live abroad, and complete three tasks chosen by her father.

The three tasks from Jessi's father are revealed: one related to the past by playing basketball together; one to the present, seeing Jessi perform; and one to the future, organize a pretend wedding.

The sister's fufill the two first tasks, and start to organize the wedding.

Jessi's pretend wedding is a success. The fourth dreamer is chosen as Hong Jin-kyung, whose dream is to host her own television show.

The members then tell Jang Jin of Hong Jin-kyung's idea for her dream of a Hong Jingyeong Show. The members start brainstorming to find ideas for the show with each member asking for advice from several people. The members then present their ideas to Jang Jin, with the director deciding Jin-kyung's idea of environmental awareness in regards to health & well-being as the best theme for the show. The members then meet up with "Speech Dart" professor Kim Hyun-ah to help them in their speech as TV presenters for Hong Jin-kyung's dream. The PD then announces that the volleyball player and Olympic competitor Kim Yeon-koung would be a special guest and a "dreamer" for several episodes.

The members meet up with athlete Kim Yeon-koung, who stated her dream to be a rapper. Due to only having a week to prepare, they will be aided by "teachers", which is revealed to be Lee Sang-min (former member of Roo'ra) & rapper DinDin. The members then head out to eat at the restaurant when they began the girl group project and surprise Kim Yeon-koung with the presence of her fellow 2016 Olympic volleyball teammates. The members then try to fulfill her special dream of being a rapper.

The members meet up with Dynamic Duo and start practicing (under 10 hours) for their stage performance: a modified version of one of their well-known tracks, "Friday Night" at a well-known club at midnight.

Jang Jin then decides on the format of Hong Jingyeong Show: a movie with a fake documentary format, which he plans to enter in a film festival. The members do camera-recording trials with Jang Jin and are tasked with finding material for the show. The members then find out where their recycled trash goes to, and do a debate on protecting the environment.

The members measure the fine dust level within their surroundings while doing their own efforts in protecting the environment, from recycling to DIY eco-friendly products. The members then meet with former politician-turned-writer Rhyu Si-min in regards with Hong Jin-kyung's ideas. Jang Jin and the members then start shooting Hong Jingyeong Show's first scenes inside Seoul City Hall, with Jessi as the holder of the boom microphone. Jang Jin then informs the members that he plans to include their work in the 14th Asiana International Short Film Festival (AISFF), where they have to convince the film festival chairman Ahn Sung-ki.

As the last dreamer, Ra Mi-ran then reveals that she plans to completely use what is left of their planned money, while she relates her life story at her old house. The members then meet up with AISFF chairman Ahn Sung-ki to convince him to include Hong Jingyeong Show in the film festival, while continuing to work on the movie's next scenes.

Ra Mi-ran's 1st dream is revealed, which is to build a house. They go to a vacant building to begin the process of building a restaurant in goodwill, with Ra Mi-ran's idea being chosen. Because of the rainy weather, they can't shoot scenes for the movie, rescheduling it instead for next week instead. Jessi and Kim Sook then receive their roles and lines for the movie, as they eat out with Jang Jin. The following week they go to work on the movie's car scene with Min Hyo-rin. After debating ideas, the cast then goes to Music Bank in search of someone young who can act. They finally settle on Music Bank host Kang Min-hyuk, and go to the MC's waiting room to ask him to act for them.

Hong Jin-kyung, Min Hyo-rin, and Jang Jin are filming their "fake" documentary while the other cast members paint the interior of the restaurant. In consideration, Hyo-rin then invites actor Kwak Si-yang with whom she worked in Persevere, Goo Hae Ra, to help the remaining members. The final design and floor plan of the restaurant is completed and split into sections for further development, with the members then bargaining and listing quotations on the necessary materials on a budget of ₩3,500,000 ($3,500). On another day, Jessi's films her part in one of the sets from Mi-ran's currently-airing drama The Gentlemen of Wolgyesu Tailor Shop while Kim Sook's double-role as a doctor and a dengue patient and Hong Jin-kyung boat scene is also filmed.

Jessi, Ra Mi-ran, and Kim Sook go to make a table, which Kim Sook shows off her wood-working skills. Hong Seok-cheon comes to help with the restaurant set up. Later, the cast throw a Halloween party with Hong Jin-kyung and Jessi dressed up as cats, Min Hyo-rin as Harley Quinn, Sook as No-Face, and Ra Mi-ran as Marge Simpson. They spend the night near Gangnam Station, talking to fans and doing silly antics.

By the day of the film festival filming has been completed, and the members preview their "fake" documentary Was Will (originally Korean: 내일도 미래람면; RR: Naeildo Miraeramyeon, translated If Tomorrow is the Future). The cast then has a congratulatory dinner, and present a gift to Jang Jin as they bid their farewells to him.

The members continue with Ra Mi-ran's next dream, who has another dream of going caroling. Sung Si-kyung comes to help with the dream, and the cast goes to their restaurant to add the finishing touches with Lee Soo-geun assisting. They buy a kimchi refrigerator as a gift, and then later hold a love-counseling lesson with college students. Various students come to get help and are later set up with blind dates.

Another dream of Ra Mi-ran is revealed to be camping, and Mi-ran comes prepared with all the needed supplies. Once the cast reaches their destination they set up, prepare food, and play a version of "Never Have I Ever" with many personal questions. As the restaurant is officially opened, the cast members get to taste the food and hold the 3:3 blind date which includes Jessi's stylist. The blind date is a success, and Ra Mi-ran's dream restaurant is opened for the public.

In the final episode, the members meet up again with Sung Si-kyung to go over their three holiday songs. They record the song the following week, to be revealed in the last part of the episode. Ra Mi-ran's dream draws to an end with a photoshoot of the cast members by rapper Bbaek Ga. The photoshoot concludes with the members saying their final words to the viewers, and one last cheer by the cast. At the end of the episode, the carol album is revealed, alongside photos from each dream in season 1 of Sister's Slam Dunk.

The 7 members with different looks, personalities and skills have gathered to achieve one dream of becoming a girl group to rewrite their forgotten dreams. Sister’s Slam Dunk Season 2!

Girl group project division conference! Vocal trainer, Jang Jinyoung! Who will be placed first in vocal test out of all the members? Dance major team vs. minor team's one point lesson! Then they all head to their accomodation where they will be living together until they become a girl group!

First night at their accommodation! Somi's teen love story is revealed during the members deciding on rooms and rules! The members bare face with no makeup and weight is revealed! For homework given by the dance teachers, the practice continues until late in the night. the Result is?

Han Chaeyoung's another try at making midnight snack! All the rising girl-groups are doing a personality test, what would the Unnies' members' personality be like? The new song with members' self-written lyrics is revealed at last!

First private vocal training! Somi fell in love with the vocal trainer, what has happened during the lesson? Yewon's house is revealed! From house-warming food, pajama party to Yewon and Somi's birthday party. What is the news that shocked every member of the Unnies?

The sad stories behind all the member's success are revealed. The reason why Jinyoung's green room became flooded with tears is? The new and an added song is finally revealed. How will the members react?

1 vs. 1 speed lesson with vocal trainer, Jang Jinyoung. He picks and solves all the members problem at once! Hong Jinkyung becomes the dance centre from being in last place! The choreographers only had one week to choreograph and the dance is finally revealed! The dance ranking over turns, who became the first and the last place?

Verse 2 specialty, Kim Sook. Will she be able to sing in the first verse? The part division war begins! Who will take the part of "I feel like a fish in water?" Mr. Serious, Jang Jinyoung's dance is revealed! A meeting about the concept for the girl group outfit. What will the final concept for the Unnies?

They practise their dancing until late at night! The full choreography for the song is finally revealed! The Unnies will be performing on the stage for the 300th episode special on "Immortal Songs!" The members attempt at rapping with Killagramz!

Unnies are performing on the "Immortal Songs'" 300th episode! One on one lesson with Director Han Wonjong. The recording finally begins.

The members try on the girl group stage clothings and also reveal their own stage outfit! The sudden change in the singing parts. The recording session finally completes!

The members go to Busan trip by train! From restaurant tour to filming their own music video. They show all their cuteness and talent just for spicy rice cake! For their music video, the Unnies cast special guests on spot at the beach!

Unnies' "Right?" is revealed. They dance endlessly for the music video shoot! The Unnies also act with chameos for the storyline for the music video. They film individual scenes and then moves onto the KBS studio for the last dancing shoot. The whole music video and the song is revealed!

Unnies finally perform on "Music Bank!" What happens afterwards? Never ending tears in every scene. Jinkyung says, "What's wrong with me? I must have "Music Bank" disease or something." Everyone is so tense before performing on "Music Bank."

As promised, the Unnies perform "Right?" dance on the bridges during the commuting hour for getting 1st on music charts. Their last performance at Konkuk University festival! The Unnies give a lecture and have a talk concert with the students.