The participants are back on Jeju Island and meet again. Lee Hye-seon, Jeong Hye-im, and Kwak Min-jae from EXchange explore the Jeju sea in a submarine. Park Na-eon, Lee Ji-yeon, and Jeong Gyu-min from EXchange 2 go off-roading to a place where Gyu-min had his EX-date. Kim Kwang-tae and Cho Hwi-hyun from Exchange 3 are glad to see each other. After spending a special time, they gather at the Jeju Island house and meet each other for the first time. What kind of beginning awaits them there?

With the representative couple from EXchange Season 2, Lee Na-yeon and Nam Hee-doo in the studio as the panellists, all the participants gather in Jeju Island House and try to get to know each other. When things are about to get comfortable, the doorbell rings. New travel mates enter the house to join them. Are they exes or friends? Then the participants are told to write letters to introduce each other. With the sudden excitement and tension, how will the trip turn out? And what changes will the travel mates bring to the trip?

On the first morning on Jeju Islands, the participants get to know each other by going on a special date. The new travel mates, Lee Kwan-woo and Park Ji-yeon, choose two participants to spend the day together. Lee Kwan-woo goes on a date with two women and finds out that someone he is drawn to is paying close attention to him. Park Ji-yeon goes rollerskating with two men who have different charms. Which one of them does she find more attractive? And the rest go bowling and have fun together. What changes will the date bring to the chemistry between them?

The couples from Season 3 - Seo Dong-jin, Song Da-hye, Choi Chang-jin, and Lee Yu-jung - visit the Jeju Island House. When the night is complete with the participants from all the seasons, they watch their famous scenes from the previous seasons together. Some enjoy the thrill of the surprise event, and some burst into tears. And they talk about how their lives have changed after EXchange. Then they are told to send their first Heart-to-Heart Text to the person they want to know better during the trip. Who do they want to know better and who will be receiving texts from whom?

The couples from Season 3 each choose one travel mate they want to become friends with and go on a double date with them. Song Da-hye picks the participant who sent her a text the night before, and they all go to try partner yoga together. Lee Yu-jung and Choi Chang-jin carefully observe the chemistry between the participants and choose a couple. The participants don’t choose their dates themselves, but they get to go on a date with someone they are interested in. The repeated coincidences make their hearts flutter. Will it be okay to expect that the coincidences will lead to a special relationship?

The participants are back on Jeju Island and meet again. Lee Hye-seon, Jeong Hye-im, and Kwak Min-jae from EXchange explore the Jeju sea in a submarine. Park Na-eon, Lee Ji-yeon, and Jung Gyu-min from EXchange 2 go off-roading to a place where Gyu-min had his EX-date. Kim Kwang-tae and Cho Hwi-hyeon from Exchange 3 are glad to see each other. After spending a special time, they gather at the Jeju Island house and meet each other for the first time. What kind of beginning awaits them there?

On the last day, the participants go on their first 1-on-1 trips, where some enjoy romantic moments at beautiful spots, and some face disappointing moments with unfortunate timing. While enjoying special moments on the date, they completely focus on each other and carefully develop feelings toward each other. Jeong Gyu-min, Jeong Hye-im, Kwak Min-jae, and Lee Ji-yeon, who are on the wave of the love square, make surprising choices before the date. Emotions become clearer as time passes. And the closer they get, the more difficult things become for them. What kind of result will come from their first and last 1-on-1 date on Jeju Island?