After her easy victory over Dakia, it's time for a more difficult mission: aiding the destruction of the Entente Alliance to the north. The Alliance is being backed by the strong powers, and has equipment and training that in some cases rival the Empire. When Tanya arrives, the Alliance is striking a critical supply base with a bombing raid, and the local Empire force are too overwhlemed to defend against it. Can she get there to hold them off in time?

Tanya's new battalion is off the ground and running, and it's time for them to do their first mission: fight back a massive invasion by the Dakian Dukedom to the southeast. The enemy army numbers in the hundreds of thousands, but they've brought no air units at all, which makes them easy pickings for Tanya's highly trained force. After wiping out the enemy army, she heads straight for the enemy capital and launches an attack there.

Tanya is now living life on easy street, as a highly-respected student at the military university. She's so highly respected, in fact, that one of the Empire's chief military planners asks her for her opinion on the course of the war. Eager to show off her intellect (and hopefully land herself a cushy job in the planning department), Tanya comes up with a plan of astonishing insight and intelligence. Her idea backfires, however, when she turns out to be a little too smart for her own good...

After her stunning success with her first mission, Tanya is assigned to test a new piece of technology: a highly unstable prototype calculation jewel. This jewel offers her unparalleled power, but just using it risks her life. Tanya is determined to get out of this project and on to someplace easier and safer (like the front lines of the war), but Being X has other ideas...

The secret of Tanya's birth is revealed. Tanya was a cold and unemotional Japanese salaryman who was pushed in front of a train by a man he laid off. An infuriated godlike creature named "Being X" sent him to this world, and reincarnated him as a baby girl... with no promise that he would ever be reincarnated again. Now Tanya has to survive, because this is all she's got!

Tanya just barely manages to restrain herself from disobeying her superior officers and attacking the Republic remanents. But the Republic forces have escaped overseas, and vowed to fight to the bitter end. The Empire has been victorious, but in its victory it has terrified the rest of the world and spurred them to action. Is true victory possible at all?

Tanya's diminished smaller company attack the battalion of Allied Kingdom mages rather than retreat. Their company use their altitude advantage but suffer heavy losses, especially when Colonel Sioux uses an illegal Trench Gun.

Tanya's spectacular mission is a success, and the Republic is surrounded and crippled. But on her way back, she runs into a group of allied mages, lead by Anton Souix, the man she crippled once more. He's back, and powered by Being X, and his one mission in life is to take down the Devil of the Rhine!

The Empire is a powerful military nation on a continent that looks much like early 20th century Europe. But in this world, magic is real. The Empire is involved in a war against the Entente Alliance, and fighting a poorly executed delaying action in the northern theater. Second Lieutenant Tanya Degurechaff leads a small platoon of mages. But there's something unusual about this lieutenant... she's only nine years aold!

Naho feels relieved now that she has the support of all her friends. On top of that, Kakeru and Naho begin to get even closer. Finally, the day of the athletic festival comes. What do Naho and the gang do to insure Kakeru can enjoy the festival from the bottom of his heart?

Up until now, Naho had been doing everything the letter from the future had told her to do, but is the letter always right? The letter from the future asks Naho to make sure Kakeru doesn't run the relay race at the athletic festival, but what does Naho decide to do?

The letter from the future details the regret felt by everyone for being unable to celebrate Kakeru's birthday. As such, high school Naho and the gang pester Kakeru about what he wants until the big day. On the other hand, 26 year-old Naho and the gang gather at the late Kakeru's grandmother's house to celebrate his birthday, like they had promised in the past.

It's the last day of the school festival. Naho and Kakeru have promised to watch the fireworks together. However, just before they start, Ueda-sama gets in Naho's way. Will Naho get to experience watching the fireworks with Kakeru like her future self did?

Kakeru gives Naho a hairpin. And on the weekend, Kakeru invites Naho to study with him for the upcoming exams. As the pair begin to grow closer together, Naho gets up the courage to invite Kakeru to see the fireworks together with her at the end of the school festival.

Naho is so concerned about Kakeru’s date with Ueda-senpai over the holidays, she can’t help but seem preoccupied and unable to focus on her friends’ conversations. Ever since Kakeru started dating Ueda-senpai, Naho has found it difficult to have a proper conversation with him. Naho regrets not directly telling Kakeru how she really felt the day Ueda-senpai asked him out, but what will she do now?

In the letter, it says Kakeru won’t join the soccer club, but in reality, he does. This difference between the letter and reality fills Naho with hope, as she believes it may mean that the future is starting to change for the better. But just as she begins to think that, she has to deal with the letter detailing how Kakeru and Ueda-senpai begin to date...

Kakeru enters the soccer club as a provisional member, just as the letter says. When the topic of lunches comes up after practice, Kakeru jokingly asks Naho to make lunch for him as well. Naho finds herself bewildered by his words, but feels pushed to act by the letter from herself 10 years in the future, which tells Naho that she wishes she had made lunch for Kakeru.

Naho can't give her Valentine's Day chocolate to Kakeru. Ever since what happened on New Year's Eve, Kakeru keeps putting distance between Naho and himself. But, through all the hardships, Naho refuses to give up and fully intends to tell Kakeru how she feels. And so, the time comes for everyone to face the fateful day outlined in the letters from the past, "Kakeru's Final Day."

Kakeru moves to Matsumoto with his mother mother after she decides to move there for her own reasons. When she passes away on the first day of school after Kakeru transfers, Kakeru blames himself and thus refuses Suwa's invitation to join the Soccer club. Kakeru sees some old classmates from Tokyo, but none of them understand what Kakeru is going through. In the end, Kakeru becomes so distressed that he feels that he has no way out.

Naho got into a fight with Kakeru on New Year's Eve, and never managed to apologize to him before he passed away. At least, that's what the letter from the future says. However, Naho now believes that she's capable of dealing with whatever may come up, and faces New Year's Eve head-on.