After spending their first year of high school in peace and quiet, Haruka and Makoto run into Nagisa, a new student who was a member at a swimming club with them when they were kids. That swimming club is being torn down, so the three of them sneak in to dig up a time capsule that they buried in the back, which is when they are reunited with Rin, the fourth member of their group who left to study abroad.

Makoto and Nagisa watch with their breaths held as Haruka and Rin engage in an intense race. However, they notice that Rin appears to be have changed. At the same time, Nagisa prepares to start up a swim club with help from Rin's sister Gou.

The Iwatobi Swim Club needs one more member before it can participate in relays. Nagisa has set his sights on his classmate Rei, who is a member of the track team. Despite Rei's refusal to join, but Nagisa appears intent on recruiting Rei into the swim club.

The Iwatobi Swim Club has a full roster now.As they begin to practice, they run into a little trouble.After a certain member claims that his swimsuit is to blame, the club makes a trip to buy new swimsuits.

Haruka and the other club members decide to hold a training camp to prepare for prefectural. Each member follows his own regimen. However, Rei is unhappy about falling behind and heads back into the ocean at night to practice.

As prefecturals draw near, Haruka and the other swim club members continue to improve. Meanwhile, Rin reveals his motivations for swimming. The swimmers must now show what they have accomplished at the tournament.

Haruka, Makoto, Nagisa, and Rei swim in their individual events. Rin becomes irritated as he remembers watching them swim back in grade school. Afterwards, the four Iwatobi Swim Club members must prepare for the medley relay.

Coach Sasabe begins training the Iwatobi Swim Club for the upcoming tournament. Meanwhile, Rei is unhappy about the fact that he's the only one who doesn't know about what happened with Rin in the past. After Rin expresses his frustration, Haruka decides to tell him about what happened when they were in grade school.

After hearing about what happened in the past, Rei goes to Samezuka Academy to ask Rin what he wants. The night before Iwatobi and Samezuka leave for regionals, Rin calls Rei to explain how he feels about the relay. And then, Samezuka announces its lineup for the relay.

The Iwatobi Swim Club must win to advance to nationals. As the tournament draws near, the members get nervous. Meanwhile, Rin grows increasingly irritated. As it comes time for the medley relay, each member must find their own answer as they step up to the start line

Haruka and his friends have grown after last summer’s tournament. Amidst the hustle and bustle of training for their individual events, their daily lives continue as usual. However, a new season now approaches!

The crew ponders how to attract new members to the Swim Club. Haruka is called in by Amakata-sensei to discuss his intended career path, but as always, Haruka moves to the beat of his own drum. Meanwhile, Coach Sasabe brings an interesting opportunity to the boys…

The Iwatobi Festival has begun! Haruka and friends are fired up for the Club-versus-Club Relay Race, hoping to attract new members by putting in an impressive performance. Meanwhile, Rei begins training but is worried by the fact that he can still only swim the butterfly stroke…

In anticipation of the upcoming prefectural tournament, the members of the Samezuka Swim Club enthusiastically show off their individual abilities. At the Iwatobi Swim Club, an equally enthusiastic Gou proposes a lunchbox inspection to ensure the boys are getting the right nutrition to support their training. However...

On the eve of prefecturals, Makoto resolves himself to broach a certain subject with Haruka. As the tournament begins, the Iwatobi Swim Club is extremely enthusiastic about its prospects. But will every member be able to pass the prelims of his individual events?

Haruka and the boys have trained hard to prepare for this showdown against Samezuka. After Day 1 of the tournament, Gou and Amakata-sensei treat the boys to a fabulous, carb-rich feast and allow them to take a breather. Meanwhile, Rin is faced with a tough decision as captain of the Samezuka Swim Club. Who will he choose to swim the relay with him?

At Samezuka Academy, the hot-blooded practices continue ahead of regionals. Meanwhile, the Iwatobi Swim Club trains diligently each day until sundown. Though Amakata-sensei is concerned, Haruka and the boys insist they want to practice as much as possible before the tournament.

As the tournament continues, Sousuke finally tells Rin about how he’s passed their years of separation. Rin is concerned at Sousuke’s nonchalant attitude toward certain things and tries to speak his mind. Meanwhile, the Iwatobi Swim Club looks toward the relay final.

The Iwatobi Swim Club continues their training. However, signs of confusion seem to keep surfacing in the silent Haruka’s swimming. Makoto and the others are worried about him, but try to continue acting cheerfully as though nothing was wrong. But one day, Sousuke appears, asking to speak to Haruka…

Upon Rin’s invitation, Haruka finds himself venturing to “a certain country.” Knowing that Haruka has hit a wall worrying about his future, Rin opens up and speaks to him about his own thoughts and feelings. Afterward, Rin quietly asks Haruka what he will do about his own future...

Having faced his feelings honestly at last, Haruka tells Makoto, Nagisa, and Rei what he has decided for himself and his future. The Iwatobi Swim Club is once again fully united as they mount the starting block at nationals, ready to swim for themselves, for their friends, and now, for the future as well.

Haruka has entered Hidaka University, where he's now training with the swim club to prepare for a newcomer tournament. One day, he runs into Asahi, a swim teammate from middle school. Haruka is later joined by Makoto, who also moved to Tokyo, at a coffee shop to catch up with Asahi... and the topic quickly turns to Ikuya, another teammate they swam with in middle school. On the day of the newcomer tournament, Haruka and Asahi are in the same race for the first time in years... and the spectacle is watched by Hiyori, who calls Haruka an "inferior copy of Ikuya." After the race, as Haruka is walking through the halls with Asahi, he catches sight of Ikuya passing by..

Haruka and his relay teammates decide to hold a training camp in the summer of their second year of middle school. During the night, Haruka heads out to the pool and finds Ikuya looking up at the stars.

Rin, now living in Australia, trains hard every day with swimmers from all around the world. Then a Japanese guy shows up where his team is training, challenging each of his teammates to races and beating them one by one. Even Rin is surprised when this newcomer reveals his identity...

Haru, Makoto, and Asahi visit Shimogami University in hopes of talking to Ikuya, but even after looking all over campus, they can't find him. Hiyori, however, notices them and makes it his mission to keep them from seeing Ikuya.

With the college championships approaching, all the swimmers are training hard on their own in addition to their official club practices. Haruka is also undergoing some extra training, with coaching from the mysterious man they've been seeing around campus. Makoto is concerned about the arrangement, but Haruka assures him that he asked for the help himself

After the breakup of his middle school swim team, Ikuya decided to get stronger on his own and not rely on anyone. But Haruka, breaking out of his freestyle comfort zone to swim in the individual medley, tells Ikuya that he's not alone.

Makoto meets up with the members of the Iwatobi Swim Club who are in Tokyo for the nationals. Meanwhile, Haru continues his training.

Nagisa, Rei, and the rest of the Iwatobi Swim Club have come to cheer on their former teammates at the All-Japan Invitational. Makoto tells them the story of how ever since Haruka swam for the first time, he'd been swimming only freestyle.