The Witch's Apprentice is an ending which occurs when the player loses to Ravyn the Necromancer.
Knowing the girls are far too weak against her Mistress's power, Ravyn immediately kills the foul-mouthed Yoshida, only to reanimate her as a gagged, big-breasted zombie ninja. Looking at Eric(a) struggling to raise their wand, Ravyn decides instead to have Yoshida bring them in, so that she could turn them into her apprentice to further spread the joy of Necro-Yuri.
After just a few weeks of rewriting, Eric(a) has already forgotten about their past, but the remaining attitude prompts Ravyn to further her brainwashing. This, however, turns Eric(a) into a ditzy, useless girl who only think about eating her teacher out and then cries when she's not getting it. Eventually, as Ravyn fixes their mind and the original brainwashing fades away, Eric(a) manages to recover their intelligence and most of their personality, becoming a ruthless member of the Necro-Yuri cult - though licking their Mistress's pussy is still their favourite thing to do.