The Perverted Flower Game Over is an ending which occurs if the Cutie Knights take every cursed item in the Fey Mansion to advance, and then the player accepts Princess Anathema IV's offer instead of trying to fight her.
Princess Anathema's offer, upon seeing the Cutie Knights cursed states, is to place a slave collar upon Eric(a), the key to which is hidden within her domain. When (or if) Eric(a) can find the key, they will all be released and she even offers to cure Vini. Until then though, they will remain her slaves.
Eric(a) accepts this offer due to the doubt of their ability to win at all in their current state, despite Veronica's initial protests. Alice also grudgingly agrees with this logic, and Natalie believes in Eric(a)'s ability to locate the key. Aside from Eric(a), the Cutie Knights are immediately engulfed in a black liquid and whisked away to become faceless and nameless slaves until such a time that they are freed.
Such a deal though is of course not going to be as simple or straightforward as it sounds at first. In short order, Eric(a) finds themself engulfed into a pink cocoon and trapped in darkness while they find their body changing into something else. Eventually, Eric(a) exits their cocoon to find her new body as an alraune, a green-skinned girl with her lower body fused to a plant.
Princess Anathema quickly summons some male servants to serve the newly transformed Erica a "meal." Quickly masturbating they ejaculate semen all over her new body, and an instinctive lick over the new mess on her face has Erica ashamed to realise the taste and heat of the cum on her skin are extraordinary to the new her. Shortly after, she understands that as an alraune with an anchored plant lower body, she is rather lacking the ability to go searching for the key - a trick that Anathema feels no shame for. With a promise of daily "feedings", and no ability to run, Erica's fate as a perverted flower to decorate Anathema's garden is seemingly assured unless she can figure some way out of this predicament to save herself and her friends.