Arriving at the town of Loreon with a mutated arm, Kallen seeks help from a mage consultant. After entering a pub and identifying the person she's looking for, Kallen meets Luciano Bradley, who offers to help her under the condition that she helps him with his performance. As she agrees, it soon becomes apparent that Luciano is a wanted criminal that specializes in Blood Magic. Fortunately, she is saved by Lelouch Lamperouge, who defeats the villain. He asks her to join his guild - Knightmare Frame - in order to properly help her with her demonic deformity. Despite her painful past experiences, Kallen agrees to join Lelouch. 
Upon arriving to the guild in the town of Homura, Kallen learns that she's on a 2-week probation period until she becomes a full-pledged member of Knightmare Frame. She and Lelouch venture around the guild building, the former meeting different members until they reach for the guild master herself, Marianne Lamperouge, Lelouch's mother. After having lunch and meeting other guild members, Kallen goes to her room to find a parcel of necessary supplies, where after she goes to sleep.
Her demonically deformed right arm at the beginning of the series is in reference to the primary weapon of the Knightmare Frame her expy of the same name pilots in Code Geass; the Guren Mk.II and subsequent versions' Radiant Wave Surger.
Kallen's demonic form at the beginning of the series was actually inspired by Pride Demons from the Dragon Age series.