Previously on Iron Leaguer, Bull Armor freaks out, but is controlled by Magnum Ace. With his power under control, he’s able to bat on Genocide Screw and grab Ace’s pitching. But, they still couldn’t win the match. Ace seems to have a new challenge, on episode 5, just after the break.
Under the moonlight in the mountains, Kiwami Jurouta awaits. When a fish makes its jump out of the water, Jurouta unleashes a slash at the moon reflex, splitting it in half. He completed his Moon Water slash, the result of his calm spirit Meikyo Shisui (Clean Mirror, Serene Water).
At Dark Kings, the Gold brothers analyze the 44 Sonic. Gold Arm seems to recognize Ace’s pitching from somewhere but his memory fails. Gillot tells the coach that he ordered Section X, Dark’s investigative organization, to move, as he doesn’t want more shame coming from them. Gold Arm promises he’ll destroy Ace at the next match.
During the trainings, the kids are almost hit by a failed batting, since the protection net is an old, unreliable one. Ace warns even the coach of the dangers, as the ball could fly anywhere. Meanwhile, the Section X follows Ace’s movements. They detect a samurai leaguer, Jurouta, at the field, watching.
One of Bull Armor’s batting sends the ball towards Jurouta’s direction. In a flash, he splits the ball in half, and walks away. Afterwards, the analyzing of 44 Sonic finishes, and Sector X’s members watch it. But most of the data is still unknown, and it seems Ace has no previous affiliation. They’ll try to examine the model number by themselves.
At the temple, Jurouta finishes his drawing. He asks the priest to deliver this letter to Silver Castle’s Magnum Ace. It’s a pine and a shrike, which the priest quickly sees as a challenge invitation. But he is concerned if Ace can translate the drawing’s meaning, and it could be a way to measure Ace’s caliber: if Ace understands the meaning, the he’s one worth the challenge, or else Jurouta will go back to the mountain.
Mach Windy and the rest of the Silver Castle members are under maintenance. Ace tells Windy he’s trusting his speed for the next match. Ruri arrives with a fan letter to Ace, which everyone is curious about: a drawing. Bull sees a pine and a sparrow, but Ace identifies the bird as a shrike. Ruri tells it was delivered by a priest, and Ryuken wonders if its a spell for winning a match. But Ace feels something different, a strong will coming from the drawing. Ace realizes that it’s a challenge, and the sender is the samurai leaguer that split the ball during the training.
Before going to sleep, Ace thinks Jurouta might become a valuable ally, but it’d be inevitable to drop the challenge. Sector X takes its chance to analyze Ace’s model number physically, but the plate is burnt out, which means all data regarding his creation is gone. It seems that there are no previous records of Ace’s pitching, but there are somewhat matching data coming from forced retired leaguers. But those ones are meant to never come back active. Their only chance now is to analyze the parts, and wait for another chance.
Ace wakes up, and walks out. The coach interferes, telling him that a shrike is a proud bird, two of them don’t land on the same place, meaning that the letter is actually a challenge invitation. He tells Ace to not overdo it, since he’s now a team player.
Jurouta awaits under the moonlight. Ace steps in, and the samurai leaguer praises him for translating the meaning of the letter. The 44 Sonic exists only because Ace’s will surpasses a machine’s one. Jurouta wants to split Ace’s diabolical pitch, but Ace refuses the challenge, as the 44 Sonic is meant to be thrown at the ground. He wants to convince Jurouta to be part of the field alongside him.
Suddenly, lights lit both of them. Those are pitching machines that start shooting balls at both. Jurouta shows of his skills by cutting the balls. Ace uses his gloves to capture the balls and his cannon to shoot them towards the lights. The Sector X members are curious why he doesn’t use his equipment at the matches. With lights broken, the machines retreat.
Jurouta wonders how someone like Ace can be a target, and he knows even a serious leaguer will be hated by someone eventually. Jurouta likes Ace, as he’s a worthy opponent, and Ace accepts the challenge under a condition: if Jurouta loses, he’ll become Silver Castle’s 4th batter. For Ace, the way of the sword is within a batter box also.
Jurouta accepts the conditions. Face a face, both are ready. If the ball hits Jurouta, Ace wins. If the ball is split, Jurouta wins. Ace focuses his soul in this pitching. The 44 Sonic is thrown, but the explosion of the impact sends Ace away. As a result, Jurouta shows his broken sword, and the edge is impacted in the ball. He realizes his Moon Water slash is still incomplete, and he walks away to the mountains.
Ace asks if he’s coming back, and Jurouta confirms he will to finish this challenge. Sector X members are now aware their investigation will take longer than imagined.