As unstable as she was already, Isa had finally had enough of her parent's favoritism. Grabbing the knife she had hidden, she was ready to end her older brother's life, destroying a "crucial" piece of her family's life. Sneaking through the house, hidden well by the shadows, she found her sleeping brother in his room, as usual. She dragged him out on to the balcony which wasn't far from the ground, and slammed his head into the concrete until he was clearly passed out. Tossing him over the edge, she jumped down as well, mission near completion.
Finally, a long way away from the estate and with no guard in sight, under the cover of the deathly dark sky, Isa grabbed her large knife, standing over her helpless brother's body. She began to stab him in the heart, multiple times, over and over, losing count, screaming and yelling wildly as she did it.
Getting tired of stabbing one place, she figured that it would be even better if her parents couldn't see their dead son's face in general or at the possible funeral, she decided to stab him in the neck and through his face multiple times, separating his head and eventually limbs as well. You couldn't tell it was even a person after she finished.
After laughing over, rambling, and screaming words out to the carcass for about an hour, Isa began to think about what she had done. She knew she couldn't stay, so she decided to just leave the entire place, with nothing but her large knife. Tossing her brother's limbs and severed head into the courtyard making sure her parents would see it in the morning, she managed to escape in the night, having absolutely no regrets.
This event takes place the night Isa escapes her family's manor. She hurled the fence, and sneaked past most of the guards. She was chased by a few guards, which she lured into a corner, and shoved a knife into, killing both of them.
Tired and beat up, she found a small patch of grass later that was sheltered by leaves that she slept on. She woke up in the middle of the night, feeling cold. She eventually noticed a figure sitting beside her. They wore a dark cloak with a hood. It was hard for her to make out if either it was a man or a woman, but a deranged voice soon spoke.
Isa was scared at first, but the figure strangely offered to help her escape. The voice of a male was recognized. With little more than a nod, Isa followed the figure through the woods until they reached a small tent. The figure flipped his hood off and showed off his mess of black hair and bright blue eyes. He called himself Flux.
He offered Isa food and shelter for a few nights, until the guards found them. They escaped with effort and a few killings... Flux later sent Isa on the route to Crestfall, never seen or heard of again.
While Isa was wandering in Old City, she accidentally bumped into the Crows. Ducking for cover, she hid and watched the group. It was unknown what they were discussing, but Isa became interested Esther the most out of them all after observing the group for several hours. So, she stalked them for a few more hours, but as soon as Sasha told the group that she had felt like they were being followed. Esther told them that he thought the same. So, Isa made a run for it. And that was the last time she had ever seen or heard of the Crows.
Once Isa reached Crestfall, she payed for a spot to stay in town after earning some money... Living this peaceful life, she enjoyed reading, helping others such as the elderly, small children, and girls her age. As listed on the Isa-chan/History (Anime) page, when she was defending two young siblings from a mercenary, Joey noticed and after she defeated the anonymous figure, he invited her into the Scarf Heroes.