Goro is a young 5 year old boy who admires his Father. His father is one of the star pitchers for the Yokohama Blue Oceans, but when his father injures his shoulder, young Goro must decide what is more important to him- following his love of the game or following his Father's wishes

Goro disregards his father's advice and decides to continue training to become a future Pro pitcher. Meanwhile, his father is visited by his old friend and teammate, Shigeno. Shigeno says Honda's true abilities have always been in pitching and not batting, but Honda must decide on his own whether to continue baseball by focusing on hitting or find an entirely new occupation.

Goro meets and befriends another little boy named Toshiya, with whom he plays catch. During one of their sessions, they witness a Little League team in play and decide they want to become Little Leaguers. Goro's father forbids it due to the use of hard baseballs. Can Honda reach his son and show him the true reason he won't let him play before they lose their bond?

Due to her consistent care of his son, Goro, Honda begins to see Goro's nursery school teacher, Momoko Shimizu, in a romantic light. He makes the decision to propose to her after Goro advances from her school. Momoko is asked by Honda to take Goro out for his birthday, as he plans to celebrate it with him a day later.

Joe Gibson, a Major League pitcher, has come over to Japan due to a wealthy amount of money he is to receive. Honda decides he will hit a home run off of Gibson at all costs.

Honda is successful in his first bat against Gibson, so Gibson retaliates with a beanball to the head. Honda falls unconscious, but he later gets up and goes to first base as though everything is okay. That night after celebrating with his son Honda realizes something is wrong. As he tries to reach his son and give him one final farewell he falls unconscious again and dies. Goro tries to wake his dad up the next day to no success. He is diagnosed as dead at the hospital and Goro's Uncle steps in to take him. Goro runs to his nursery teacher, Shimizu, who has just revealed she was engaged to Honda. She agrees to become Goro's new mom and take care of him over his Uncle

It has been 3 years since his dad passed away, but at age 9 Goro is finally old enough to enter Little League Baseball. He returns to the field of the Mifune Dolphins, but when he arrives he learns they only have 5 players and that the team could be folding. To make things worse the soccer club has gotten permission from the city to fully take control of the field. The coach recommends Goro goes to the other Little League team in the city, but Goro is determined to play for the Dolphins and begins recruiting his classmates to play.

Sawamura decides to get rid of Goro's mitt after Komori decides to play baseball. Komori decides to confront Sawamura about it and is able to prevent the mitt from being thrown into the neighboring river. Neither realize that Goro has followed the two of them. Goro confronts Sawamura about his lack of thinking about people's feelings. After realizing Komori is indeed his own individual Sawamura goes and apologizes to him and Goro. Afterwards he asks permission to join Mifune's baseball.

Mifune begins playing the adult sandlot team in an effort to get privileges back to play on the field, but Goro's new teammates aren't sure if they should trust this arrogant rookie who has never practiced with them before.

The adult sandlot team has been taking it easy on the kids. When rain begins to fall the city wants them to call the game and give the adults the win, but the sandlotters are determined to let the Little Leaguers have this one shot at glory. Can Goro keep pitching control in the rain?

Despite gaining the ability to practice once against, the Mifune coach insists Goro go to Yokohama Little Leagues field at least once. Goro learns his old childhood friend, Toshi, is now the starting catcher, and he also learns his father played for Yokohama. Will Goro betray his team to join the one his father played for?

Goro is sent two tickets to the All-Star game by Gibson. When his mom gets sick he invites his friends. The three hold a drawing and Shimizu wins it. Along with the interpreter the two go to the All-Star game. Shimizu accidentally breaks Goro's arm during the trip. At the game Gibson states he will only pitch fastballs. He manages to strike out the side for the three innings he pitches. Afterwards he invites Goro and Shimizu down to let Goro get his revenge by beaning him, but Goro asks Gibson to wait until he gets older because he can't pitch and he thinks Gibson has a lot to provide the fans of the world.

Despite his injury Goro convinces the coach to take them to a baseball summer camp where all the top teams from the area are participating. Goro is determined to build up some of his teammates abilities as well as his own experience by playing the best, but will it destroy their self esteem instead?

Goro quickly lets his pride get in the way and challenges the #2 team despite his injury determined to strike them all out. As things begin to develop though Goro hits a batter and starts to get the yips. Can Komori help him overcome this new fear?

As the summer camp comes to a close, the Coach decides if his players truly want to defeat Yokohama Little League he must put off his fear of being too nice while coaching and make them pass a timed run up the neighboring hill.

As the team begins their run up the neighboring hill Goro and Komori are easily able to pace themselves, but the rest of the team has doubts and contemplates quitting. The problem is if even one player quits, then Mifune won't be able to play in the upcoming Little League Tourney.

Mifune believes they have the talent on the pitch and in the top of the batting order with Goro and Komori, but when they learn they are going to play one of the previous years eight finalists to start the Little League Tourney they must try to overcome the mistakes they make themselves if they hope to have any chance to advance.

After being uncertain how to approach Goro, Momoko turns to Hideki for some fatherly advice, but when Goro sees the two together he begins to have nightmares about Momoko abandoning him while the two of them getting married. Will Momoko be able to approach Goro, especially when he turns against any advice Hideki tries to give him?

During the second game in the Little League Tournament Komori falls and sprains his wrist while batting. With no one else able to catch his fastballs Goro is forced to take over the catcher's position and Sawamura becomes the games pitcher. The problem is Sawamura doesn't have any game experience. Will Goro's plan to make Sawamura the backup pitcher backfire on him?

Sawamura comes up with the idea of a vertical bunt to ruin the perfect game Kyuta has going. Goro decides to have the next few batters feign vertical bunts and loads teh bases. When the opposing coach decides he wants to remove Kyuta for showing emotions, Goro challenges him and is surprised to learn the umpire sides with him. Kyuta remains in the game and decides to have a one-on-one battle with Goro. Whichever player wins this battle will move their team on to the showdown with Yokohama Little League.

Komori's sprain will keep him from catching for a month, so the rest of the team is forced to try and catch Goro's pitches. None of them are able to do so, but Shimizu has enough determination to where she says she will spend all week learning how to do so. This day before the match after their final practice both Toshi and Ryoko Kawase approach Goro. They inform him they won't be in the starting lineup and aren't sure they will be able to play against their greatest rival. Goro sees this as a challenge and decides to do everything possible to get these two on the field at the next days game.

Trouble begins immediately for the Dolphins when their coach throws out his back. Luckily Momoko has come to the match to watch. The team calls her in, and she becomes the temporary coach. However Momoko doesn't know what she's doing, and even though he is there Hideki can't help her. The Dolphins are determined not to lose, but can they really beat the defending champs and their crosstown rivals?

Yokohama manages to get an early lead off of Goro, and Toshi seems to be leading them to a shutout. Goro is determined though to rally his teammates spirits by starting at the batter box and to not let his Father's picture see a disgraceful game result.

Exhaustion has come upon Goro, and Hideki realizes that Goro has stopped pitching normally as a result. If Goro continues to pitch the way he is, he will throw out his shoulder and ruin any chances he has of playing baseball in the future. However Momoko doesn't want to stop him because they all appear to be having fun and they realize this could be one of their last games together. What will be the ultimate result between Yokohama and Mifune now that all the main players are out?

The injury to Goro keeps him out for two months and ruins the Dolphins chances at winning the Little League Playoffs. The team however hopes to build on the momentum they have had, but little do they know the marriage between Hoshino Momoko and Hieki Shigeno is going to result in a change that could influence all of their futures.