3-1 Main Story: Birdcages (Library Summaries)

1
A small girl and a giant man walk through a deep, unfamiliar wood.
They do not understand what is happening to them, nor why they are there.

Eventually, they arrive at an altar. It sits bathed in dappled sunlight,  with a sword plunged deep into its heart. As they stare at the blade, a figure emerges from it: it is a projection of the sword's past wielder,\none who speaks of the many victories he achieved with the weapon.

When the figure is finally satisfied with the telling of its tale, a white ghost collects the sword and leaves. This ghost is a creature the girl and her friends call "Mama," and her objective is to collect every weapon and store it away for safekeeping.

Girl and giant proceed, avoiding the strange pillars that appear as the weapons are collected. They follow Mama, believing she knows something, and eventually come across a beautiful, yet unearthly, sight. Without a second thought, the man loudly proclaims he knows this place, and that it is what the location called The Cage once looked like...

2
For years has this battle raged. Dark foes attempt to infiltrate the paradise world, and the people resist. But the people can only do so much, and they are all eventually captured and placed in cages.
Now, defeat feels all but inevitable.

The girl finds a cage bigger than the rest with a familiar figure sleeping inside: a dark monster. This stirs memories that had been buried deep—memories of a precious friend she met in a dream. But when she attempts to save the monster, she finds it is but illusion.
Still, she knows the monster is out there somewhere, so she decides it is her turn to save him.

As the pair hurries on, their vision is covered by a great flock of black birds. As the creatures pass, the scars of battle grow deeper and more severe, until finally the scenery collapses before their eyes. They continue in this way for some time, until a set of stone towers finally looms up before them. This is when they finally understand: the moment the dark foes destroyed paradise,  The Cage as they knew it was created.

3
Subjected to constant attacks, The Cage lies on the brink of collapse.
And while the hearts of the girl and giant ache for all the lives lost, they bravely press on. Though the incandescent tumult of war hinders them, the girl is driven by her desire to save the monster, and the giant by his need to support her.

When they at last arrive in the depths of The Cage, they find a white-haired young woman facing off against the dark foes.
They join in her fight and beat back the enemy together.

After savoring their victory, the girl asks if the woman has seen a black monster, and is surprised to hear she has. Alas, the girl's delight is quickly interrupted by a swarm of black birds. The giant sees them coming and bravely stands in front of his companions, telling them they must save the monster at all costs.
When the swarm finally departs, he is nowhere to be found.

4
The young girl and white-haired woman muster their courage to save the monster and giant. The girl bears through the feelings of helplessness that plague her, and finally locates the monster's cage in the depths of a hellish prison. Standing before him, she begins to pray, knowing in her heart of hearts that she will do anything to save him.

As she does so, another flock of black birds explodes into view, bringing the giant with them. It turns out Mama has brought him back, and he now stands ready to help the little girl.

The three of them stand before the monster in his jail. As they do, a small black bird appears—one that appears to be as afraid to find themselves in The Cage as the girl is.
When she pats it on the head and it returns to its birdcage, the monster is similarly freed.

Noticing that the monster has lost his memories, the little girl proclaims that they will make new memories together once more.
They then join hands and march towards the door that appears before them; with each of them having reclaimed something they wish to protect, they no longer have any doubts.