Lost in the Cruel World (Visual Novel)

Lost in the Cruel World is a visual novel by Hiroshi Seko. It was first released on September 18th, 2013 in Japan bundled with the third anime Blu-ray. The story was also included in the novel Attack on Titan: Lost Girls which was later adapted into a manga of the same name.

Part One
During the battle of Trost District, Armin Arlert informs Mikasa Ackerman that Eren Yeager has been killed in battle alongside his comrades. With a lost sense of purpose, Mikasa speeds through the city killing Titans until her Vertical Maneuvering Equipment runs out of gas, sending her falling to the ground below.

As she lies in a daze, having fallen onto a shop awning, Mikasa is filled with regret at her inability to save Eren and distaste at the biting cold brought by a light rainfall. Looking up at the gray sky, she sees a white butterfly fluttering across the battlefield. She grows upset, blaming the rain for the tragedy of that day since hardships in her life have always been accompanied by rain. Before her grief can consume her, she stops herself from thinking.

Part Three
Back in the chaos of Trost, Mikasa opens her eyes to the gray sky. The light rain ceases, and the white butterfly disappears with it. Feeling as if she had awoken from a long dream, she realizes that it is in Eren's nature to fall into death's grasp despite her efforts. Her grief sets in, and she laments having lost her family again. Setting herself on the ground and kneeling in the street, she decides to surrender her life to the Titans. But as a Titan reaches for her, she defends herself and wards off the Titan despite not knowing why. As another Titan appears behind Mikasa, she remembers Eren's words to her when his life was nearly taken by one of her kidnappers. Vowing to fight in memory of Eren, she lets out a battle cry.

Part Four
As Mikasa prepares to fight, the Titan behind her swings its fist at the one in front of her. Staring in awe at the sight before her, an embodiment of humanity's fury, Mikasa wishes on the rogue Titan for her to see Eren again.