Following the Ryoyukan match which concluded S1, Shinkoshigaya went up against Kumajitsu, another powerhouse highschool with a high-scoring, offensively-oriented playstyle and a hotblooded top batter who doubled as their ace pitcher with the fastest fastball in the prefecture (but poor ball control). Yomi came through with her pitching while Risa-senpai stepped up at bat, earning Shinkoshigaya the win and a best 8 spot in the prefectural summer tournament.
However, Shinkoshigaya come up next against Yanagigawa University Affiliated Kawakoshi High (who they tied in the practice game in episode 4). Yanagigawa has refined their defense even further as Oono, their lefty 3rd year regular pitcher, shoulders the burden of it being the 3rd year's last tournament. Her "final game" pressure gets the better of Nozomi at bat, ending Shinkoshigaya's first tournament run.
Following Shinkoshigaya's tremendous and unexpected success at their first tournament, the team wins some welcome popularity/support at school (though they are still snubbed by the upper years due to the past scandal). In particular, the coach is able to negotiate a bus for transportation to practice matches during summer vacation and a new character, a short-statured second year lefty pitcher who played in youth leagues but wasn't part of the school team during the previous scandal, joins the club (Kawahara Hikari).
As Hikari acclimates to the team and Yomi takes on the challenge of adjusting the form of her "special" pitch and her newly acquired super fastball so that they can't be told apart at time of release, Shinkoshigaya go through a training camp and series of practice matches in preparation for the Autumn Tournament. The Autumn Tournament is a regional tournament in Japan which is nonetheless important as the proving grounds for the new generation of 2nd Year highschool teams after 3rd years have retired from club activities, and also acts as a qualifier for the Spring Koshien tournament, which shares status with the famous Summer Koshien.
In particular, during the practice games Ryou takes on the challenge of converting to a lefty hitter (at the suggestion of Nozomi) while Nozomi also struggles to overcome the trauma of having lost to Oono's slider in their final game of the summer tournament. After several games of angst and middling performance, Hikari (who happens to also be a lefty pitcher with a powerful slider) takes the drastic measure of proposing a direct showdown with Nozomi to help her get over her trauma. After a grueling series of at-bats (with the whole team present as fielders), Nozomi finally gets in a good hit, allowing her to return to her previous form and truly welcome Hikari as a member of the team.
Shinkoshigaya then heads into the Autumn tournament, winning their first game with ease. For their second game, they face a young/inexperienced team who got a win for the first time after the transfer in of two experienced players who left Shinkoshigaya the previous year following the scandal. Although the transfer students were forbidden to play in official matches for a year, they proactively took part in coaching and had already become the center of the new team. Rei and Risa faced their old teammates, acknowledging the struggles of the different paths/choices they had each taken but ultimately finding comradery in their continued love for baseball.
Shinkoshigaya advanced, now facing an up-and-coming team anchored by a genius-level pitcher. Hikari is the starting pitcher, as Shikoshigaya now has the leeway to rotate pitchers and rest them in alternation, while the ace of the opponent team has continued pitching for every game. Although Shinkoshigaya earns the first runs, gaining an early advantage, the opponent pitcher learns from Hikari's form, adjusting her own throws to evolve her form within a single game (a feat which Yomi had been struggling the whole summer to achieve). Shinkoshigaya manage to run away with their early lead thanks to solid defense but end up not adding to their score.
As they enter the quarterfinals bracket, for the 4th game of the Autumn tournament, Shinkoshigaya faces off against Sakura High, the prefectural winners of the Summer tournament. Just before the match begins, Yomi visits the restroom and happens to come across not only the catcher from her middle school team (who only played baseball "for fun" and thus couldn't catch Yomi's special pitch, ending their middle school record with zero wins), but also a senpai who had transferred out of Shinkoshigaya after the scandal, both of them as support (i.e. not even benchers) for Sakura. Although the catcher was concillatory, saying that she had realized she liked baseball after all and was glad to see that Yomi had continued, the senpai (who Yomi did not directly talk to) was dismissive, saying that Shinkoshigaya's successes were a fluke/possible foul play and that Sakura would trample them.
Yomi, who had been quietly carrying a lot of stress/dissatisfaction over many different issues (the prejudice against the baseball club from older students at school; the difficulty of changing/improving her pitching form; the resulting displacement of her ace pitcher position in the team with the arrival of Hikari, who on top of having more stable results could also bat), snapped with this disrespect against her senpais and decided she needed to crush Sakura in order to clear the Shinkoshigaya baseball team's name once and for all. Returning to the team, she quietly told Tama that she wanted to throw only her special pitch and the super fast ball (as opposed to the other two breaking balls she could also do reliably) in order to achieve a perfect game (in baseball, that is a game in which no opponent runner ever makes it to base) against the summer champions.
Standing on the pitch, Yomi gives off a dark/heavy aura (her intensity is compared by Sakura's top players to that of 3rd years in their final tournament) and she heightens her focus to the point of completely perfecting her form. Via its extreme movement, her special pitch even intimidates the opponent batters, making them flinch/cower instead of swing, because the ball's initial trajectory appears to head straight for their face. As the field becomes covered in rain, Yomi completes the first 3 innings (9 outs) with 0 runners and 5 strike outs, barely even letting the defense contribute because the batters are struck out at the plate.
Almost all of the team quickly notice Yomi's peculiarity and become concerned because she is straining herself beyond her limits. Besides pitching, when Yomi's turn comes up at bat, she hits a triple (ultimately winning Shinkoshigaya the first point of the game with a full sprint off of a sacrificial fly) despite her typical performance being comically poor with a 0.1 On-Base Percentage. Tama notes that it seems like Yomi is trying to win the game "all by herself" -- similar to the way she cornered herself during the first practice match of the series -- forgetting that baseball is supposed to be played by a team.
As Yomi begins going through the opponent's second batting cycle, it becomes harder and harder to maintain her ideal, as Sakura quickly noticed that Yomi was restricting herself to only two pitch types and adopted strategies to wear down her stamina moreso than trying to get on base. In the 4th inning, Tama smartly leads Sakura's batters into hitting into predicted zones of the defense in defiance of Yomi's goal, which was to suppress Sakura through sheer pitching power. For the last out, against Sakura's top batter, Tama gives Yomi the signal for a Cutter instead of the signature pitches she had been using thus far, tricking the batter into swinging early against an easier pitch at the cost of breaking Yomi's will to achieve a perfect game via pitching alone.
As the game enters a 15 minute break before the 5th inning, Tama sits down with Yomi in the locker room for a heart-to-heart. She asks Yomi to explain the circumstances and her intentions (Yomi felt she needed to overwhelmingly beat Sakura at any cost; she didn't want to burden the rest of the team with nasty gossip; she thought that even if she over-burdened herself and couldn't play baseball anymore, the team had Hikari so they would be okay). In response, Tama stated that Yomi shouldn't try to carry everything alone because the team each had their own thoughts/resolutions regarding the school/scandal and would be happy to carry the burden with her. Although Tama would happily be Yomi's partner in any other activity (soccer, volleyball, mahjong?), she was still fond of baseball because she started it in the first place to catch Yomi's pitches.
Entering the 5th inning, the weight on Yomi is lifted and Shinkoshigaya continues the perfect game by mixing in Yomi's additional pitches and smartly positioning their defence. As they enter their offense phase however, Yomi is switched out for Hikari in order for Yoshino to check Yomi's condition and give her a chance to rest.
In the 6th inning, a fresh Hikari and Shinkoshigaya's fielders provide a great defense and manage to keep Sakura at zero runs. Rei, Risa, and Tama step up in the offense phase, bringing in two more points. Shinkoshigaya's defense remains solid in the 7th and final inning, keeping Sakura shut down for the last 3 outs, concluding the match with a 3-0 scoreline against the summer champions. Volume 11 concludes with a 5 day break before Shinkoshigaya's next match in the tournament, the Autumn semifinals against Misono Academy, another powerhouse school.