"Firefly" is episode 115 of the Berserk manga series.
Synopsis[]
A flashback shows Rosine's first finding of the Misty Valley. Wearing only a tattered dress, and holding her as-of-yet unused beherit, she gleefully runs headlong into the place that would become her home.
In the present, Rosine has flown into a rage, screaming that an elf should never be harmed by a human. As Guts falls to the ground, Rosine spins around and charges straight at him, her whip outstretched like a spike, intending to impale him. He cannot dodge while in midair. Guts notices the spike at the last second before it makes contact, drawing blood. Rosine's victorious face slowly fades when she realizes that Guts turned his head at the last second.
Being stabbed in the face is not enough to stop Guts.
She has indeed impaled him, but her spike has gone through his cheek, passed through his mouth, and protrudes out his other cheek. Lost in his wrath, Guts bites down on the spike so that she can't escape his next attack - a swing from the Dragon Slayer straight down over her head, cleaving her torso nearly in two and severing her left arm.
As Guts falls back to the ground, unconscious, a fluttering Rosine has forgotten about her pain. She thinks back on how her parents were never there for her and how they were the reason she was driven away. She sat alone in the Misty Valley, knowing full well elves didn't exist, but maintained the illusion that they did to justify her leaving the village. One day, her parents found her sitting alone by the lake inside her paradise home. Her mother hugged her lovingly, but her father struck her, berating her decision to leave. He yelled about how humiliated he was that the villagers troubled themselves with finding her after she left. He asked if she had left due to his not being her real father. Her mother intervened, but he turned on her, striking and beating her like he did to Rosine. As she watched, Rosine decided that such behavior was not allowed in the valley and hoped for them to go away. The blood pouring from her mouth dripped onto her beherit, which activated.
In a twist of fate, it turns out that Rosine was correct in believing that elves are real.
Guts has fallen into the lake below while Rosine has fluttered back to her cedar tree headquarters. She lays on her back, in her most human form once again, left arm gone. She silently begs for her parents' forgiveness. As Jill runs over, concerned for her friend, Rosine admits that the elves were never real. Puck flies in front of her face to introduce himself properly, saying that he is a real elf, and that elves really did live in the Misty Valley long before Rosine made it her home.
As Jill holds Puck, Rosine reaches out to touch him, the first real elf she's ever seen. As she does so, Guts bursts out of the lake, still overcome with wrath.