It follows Minato Kiyomizu, who wakes up 203 days after a car crash with no memory of the last three years. He quickly learns that, though he has no recollection of it, he was a star water polo player in junior high. Though he resists at first, fate conspires to make him pick up the sport again when he enters high school and joins a team that was resurrected after ten years, only one year earlier, by the captain, Jo Jojima.
However, the team face challenges from the very beginning...
Re-Main contains examples of:
- Affectionate Nickname: Jojima, The Nicknamer, calls Inomata "Babi", Ushimado "Ushi", Eijiri "Buu", and Amihama "Ami-Ami." He also nicknames himself "Jojo."
- Always Someone Better:
- Amihama sees his own brother as The Rival and someone he is unable to defeat in swimming.
- Momosaki sees Minato as his rival since their middle school years, and when he finally gets Minato's former playing position, he still becomes frustrated because his coach would often compare Minato to him.
- Amnesiac Hero: Minato loses the memories from the last three years (basically his entire middle school life) from a car accident. In episode 8, he regains them, but after another head injury, he loses memories of the past year when he was in high school.
- Anger Montage: Minato gets his middle school memories back in episode 8 but loses his high school memories. He becomes resentful of his life and everyone in it—including his parents, his new friends and even the medical staff that tended to him— and has a mental breakdown after his former coach rejects his request to have him return to either Shogakukan's team and the school itself. After coming home, Minato proceeds to trash his room, destroying anything related to water polo.
- Art Shift: Sometimes the art will be shifted into crayon drawings, which are indicative of Minato's child-like personality. These stop appearing once Minato gets his middle school memories back.
- Bad "Bad Acting": When the water polo team attempts to convince Amihama to join, they pretend to have very forced and unconvincing conversations about how great water polo is around him. Special mention goes to Eijiri who apparently has No Indoor Voice when acting.
- The Bet: Minato learns from Chinu that he once made a bet with her that if he won the nationals, she owed him a kiss; she holds up to that promise. She also claims that he made another bet with her that if he became Japan's top water polo player, she would date him, otherwise he would have to pay her 220,000 yen. The second bet turned out to be a lie, though.
- Bittersweet Ending: Minato and his new team failed to defeat his old team at the prefecture game, but the results finally changed Minato's viewpoint of the sport for the better. He decides to continue on doing water polo and making good memories with his friends and family while still acknowledging and learning from the mistakes he made prior to the car crash.
- "Blind Idiot" Translation: In-Universe example: Jojima has "Yamanami Water Ball" in English printed on the back of their team jerseys.note Eitaro, however, points out three times that the sport is called "water polo" in English, not water ball.
- Broken Ace: Minato was one of the greatest water polo players in Japan before his amnesia. He was also a hard-core Jerkass. Nobody is pleased when the jerkass comes back.
- But Not Too Foreign: Inomata is half-Japanese and half-Nigerian.
- Can't Catch Up: After getting his memories back, Minato personally goes to meet his former coach to request that he return to Shogakukan High School. The coach points out that because Minato missed out on a year's worth of training, especially during his formative years, he would not be able to keep up with the intensive training that the team does daily, nor will he be able to catch up to the skill level of his former teammates. He's also unable to re-enroll back to the school itself to further drive the point home, which is what gets him to snap and disavow everything related to water polo when he returns home.
- Cerebus Retcon: After The Reveal in episodes 7 and 8, it's much more easier to sympathize with Eitaro for lying to Minato about them being friends in the past. In addition, it also puts a different light on Minato and Chinu's relationship, with Chinu revealing she has always hated Minato for his arrogant attitude and for treating her Childhood Friend poorly. Last, but it also paints the scene right before the car accident differently, where Minato is shown blatantly ignoring Asumi when she is talking to him.
- Cerebus Syndrome: At the end of episode 7, while re-watching a recording, Minato suddenly realizes that he was a Jerkass in middle school the entire time. It gets even worse in episode 8 when he suffers another head injury that lets him keep his middle school memories but lose the past year of memories he spent at Yamanami High School.
- Club Stub: The water polo team consists of seven characters - the exact number needed to field a team - and it struggled to recruit that many players as it was. In the previous year, Jojima was able to find six other members initially but then they all quit, leaving him as the only member.
- Color-Coded Characters: Particularly obvious in the OP.
- Minato is blue.
- Jojima is yellow.
- Eitaro is green.
- Inomata is orange.
- Ushimado is purple.
- Eijiri is red.
- Amihama is black.
- Deadpan Snarker: Minato usually runs some snarky commentary in his head.
- Everyone Is Related: Amihama's older brother is none other than Momosaki, Minato's middle school classmate and former teammate.
- Evolving Credits:
- During the ending credits in episode 7, the selfie Minato takes with his water polo team from the previous photo is now framed next to his middle school photo. In episode 8, there is now a glare over the middle school photo.
- Beginning in episode 8, during the opening, Chinu is no longer smiling when Minato bikes past her.
- Extreme Doormat: Ushimado is very shy, and he later reveals that he joined the water polo team because his classmates urged him to join as a joke. However, he ends up liking the sport and his team for real, so he decides to stay.
- Fanservice: Much like Free!, the eye candy is exclusively from the male cast, all of whom are athletic swimmer boys who spend half their time being shirtless.
- "Flowers for Algernon" Syndrome: During middle school, Minato's coach eventually shaped him into being a selfish jerk. However, he suddenly reverts to his idealistic self after losing memories of the past three years. When he gets his memories back but loses his most recent ones, he becomes angry after learning that he has lost the opportunity to further his water polo career at his peak, and that both his own sister and Chinu prefer his memory-less self over who he had always been.
- Foreshadowing:
- Minato’s concerns in episode 6 when he confesses to the team that he’s worried about losing his memories of them if his old memories come back are not entirely unfounded. Yes, he keeps his new memories when his old ones return, but tragically in episode 8, after another accident, his old ones stay, but his new ones are gone.
- In episode 1, Minato is seen ignoring Asumi during her flashback of the car accident, which hints at Minato's arrogant behavior in middle school.
- Gentle Giant: Inomata is very tall but he's also kind and soft-spoken, easily being the nicest characters in the series.
- Hard Work Hardly Works: Minato never actually had natural talent in water polo as some people have hyped him up to be. He was only good at the sport because he studied it vigorously and took extra steps in practicing, such as recording himself. So, when he gets his memories back and learns that Shogakukan won't let him come back to the team, he feels very frustrated.
- Height Angst: A little from Inomata - because he's tall, people always assume he'll be good at sport and he's not.
- Heroic BSoD: Minato goes into shock when he remembers he used to be a Jerkass in middle school, which led him to become so distracted he ends up having another head injury that makes him lose his high school memories. He goes through another mental shock after realizing, as his old self, that he had been hospitalized at a critical time in his water polo career and that he could no longer regain the time he had lost while in a coma. Moreover, after his former coach tells him that he can't accept him back onto Shogakukan's team, much less the school itself, he starts destroying his room.
- Hostile Weather: The accident that kicks off the series takes place during a moderately wet afternoon. The hostile part kicks in when a truck comes out of nowhere, forcing Taeko to slam on the brakes and skid into a lightpost right where Minato is sitting. After he wakes up from his second head injury, he calls out Taeko on this after she reveals to Minato what happened, resulting in him refusing to even leave his room in anger once they return home.
- I Hate Past Me: In episode 7, Minato finds a recording of him yelling at his team in middle school and learns that he was a Jerkass. He becomes horrified and frightened upon discovery.
- Large Ham: Amihama is The Stoic, but every time he is called on to read a passage in class, he reads it passionately and with fervor. Minato notes that if he finds something worth his time, he'll dedicate his fullest to it.
- Lying to Protect Your Feelings: The water polo team initially decides to trick Ushimado into practicing with lighter weights and practicing tosses from shorter distances in order to boost his confidence. Only Amihama opposes this, as he points out that misleading Ushimado about his actual skill level is detrimental.
- Malaproper: Minato has a habit of mispronouncing words without realizing it, such as "hendy" instead of "handicap" and "lezz do this" (yattarudo) instead of "let's do this" (yatteruzo).
- Manipulative Bastard: In episode 5, Eitaro reveals that he and Minato were never as close as he pretended they were in middle school, and that he took advantage of his memory loss to urge him to take on water polo again. Given that Minato was actually a Jerkass in middle school, it makes sense why he would feel he would need to do that.
- Mistaken for Suicidal: In episode 6, Ushi starts feeling down on himself that he isn't making any improvement during the team's training camp, and when he disappears, the water polo team immediately assumes the worst. Minato finds Ushi in a classroom and assumes that he is going to hang himself, when in reality he was just fixing a clothesline that fell from the ceiling.
- Naïve Newcomer: With the exception of Jojima and Eitaro, Minato (post-amnesia) and the others are beginners at water polo.
- Opposing Sports Team: Kadokawa High's water polo team is a perfect (although non-villainous) example. The coach is a Drill Sergeant Nasty who is single-handedly responsible for Minato becoming the Jerkass he was before the amnesia (by telling him that being the team's ace meant being aggressive), refuses to allow Minato to become part of the team again because he doesn't think Minato would catch up to his teammates' Training from Hell, and Amihama's brother reveals to Minato that he, the captain of the team, is The Unfavorite of the coach with Minato as (ironically) the favorite the coach keeps comparing him to.
- Parental Neglect: Jojima and his father ignore each other at home, but it's out of consideration and not out of malice: after the death of his mother, Jojima tried to lift the burden from his father by making his own food, but it ended up making his father hurt. The fact that Jojima's father is too busy with work to see him often also made them drift apart.
- Minato accuses his whole family for doing this to him when Takeo comes out and reveals what happened between the the two accidents in Episode 8. He refuses to acknowledge, let alone speak to them afterward because of it.
- Ragtag Bunch of Misfits: The team is made up of an amnesiac star player with no memory of the sport, the underclassman who followed him to a no-name high school, a captain who was the only person on the team the year before, a tall kid who's never been any good at sport, a boy so shy that even when he does talk he doesn't seem to want anyone to hear him, a guy who couldn't even make the bench in the baseball team, and a star swimmer whose entire motivation for sport revolves around beating his brother.
- Real Men Cook: Inomata's father is a pastry chef and he thus knows how to make sweets.
- Red Oni, Blue Oni: True to their thematic colors, Eijiri is hot-headed while Amihama maintains a composed demeanor. The two often get into arguments over their playing styles.
- Shrinking Violet: Ushimado is very shy and hardly speaks above a whisper.
- Sibling Rivalry: Amihama only decides to join the water polo team as an opportunity to defeat his brother, who outperformed him in swimming. When they were little, they also promised to have a Friendly Rivalry, at least, up until his brother decided Minato is his new rival.
- Smart People Wear Glasses: Eitaro is very knowledgeable about the rules of water polo and wears glasses.
- Solomon Divorce: Amihama's parents are divorced, and he lives with his father while his brother lives with their mother.
- Stalker without a Crush: Eitaro literally followed Minato to Yamanami High School and chased him around to convince him to take on water polo again.
- Stepford Smiler: Jojima is cheerful and silly, but he also has a very awkward and strained relationship with his father.
- Title Drop: In the first episode, Minato sees that he had underlined and annotated the rule "re-main" in one of his water polo textbooks. It gets brought up again in episode 4 when Momosaki rephrases the word with the meaning of "becoming a main character (player) again." Hilariously, Eitaro later points out that the term "re-main" is outdated and it's known as "offsides" today.
- Took a Level in Jerkass: At the end of episode 7, Minato learns that he was a Jerkass in middle school, and Chinu confirms it in episode 8. Even worse, Minato gets another head injury that lets him keep the middle school memories and lose the memories he created at Yamanami High School, meaning that he keeps his original, arrogant personality.
- Trauma Button: The car crash is one to Minato's younger sister Asumi, who witnessed Minato take the brunt of the injuries, to the point of having nightmares of it. It's implied that this is also true with Minato's mother Taeko, due to being the one driving that day.
- Used to Be a Sweet Kid: Minato is gentle and easygoing, which was how he was like in elementary school. After getting his middle school memories back and losing memories of his new life, he turns back into the cynical, arrogant person he had previously grown to become.
- Walking Shirtless Scene: At least half the anime is shirtless high school boys.
- Walking Swimsuit Scene: Unsurprisingly considering the focus on water polo, a big number of the series' scenes has the male members of the cast in swimsuits.
- We Want Our Idiot Back!: Asumi prefers Minato's memory-less self, as he is much kinder to her compared to how he would ignore her in middle school. Likewise, it's implied Chinu does as well — she hung out with him even after she confessed to him that she hated him, and it's only when she discovers that Minato has lost his most recent memories that she decides she will no longer talk to him.
- Wham Episode:
- Episode 7: At the end of the episode, while re-watching a recording, Minato suddenly realizes that he was a Jerkass in middle school the entire time.
- Episode 8: After cycling home in the rain, Minato suffers another head injury that lets him keep his middle school memories but lose the past year of memories he spent at Yamanami High School. He also ends up lashing out at his family for lying to him all this time, then tries and fails to get re-enrolled back at his old school and water polo team, causing him to have a complete breakdown and begin trashing his room.
- The Worf Effect: Minato was one of Japan's top water polo athletes in his age bracket; however, after experiencing a car accident, he has lost all memories of when he was in middle school, including water polo. His muscles have atrophied and he no longer has any knowledge on how to play, so he must start from scratch again.
