First of all, the core of your game is that the protagonist dies after a tragic life and then returns to the past—she’s determined to change that known tragic future, and only once all the chemistry between the characters and their interwoven relationships comes together does the story feel complete. Adding a bad ending for the protagonist in this kind of time‑travel game is inherently strange. Since she’s already gone back expressly to avert that tragic future, giving players choices that lead to an even worse bad ending under that premise really doesn’t make sense.
Besides, you’ve already invested a huge amount of time and effort to produce a high‑quality game; there’s truly no need to spend extra resources on a storyline that doesn’t align with the main narrative. If you really want to include it, you could simply hint at it through memories of a past life. And if you want to heighten the game’s tension, just add one extra CG.
Alternatively, you can diversify the endings by exploring different relationship routes between the protagonist and the other characters—such as a harem ending, a solo ending, a true‑love route, a corruption route, and at worst a friendship route.