My Yandere Girlfriend Is Extremely Possessive Of Me

(WARNING: Contains a lot of gore and death later in the story, its really dark. The death meaning to side characters, not the female nor male lead.) (As for the romance, I'm going to focus just on the female and male lead, no NTR, no love triangles, and no harem.)
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After a certain incident in his childhood past, Haise Kirishima became traumatized and becomes isolated, away from interacting with others. Because of this incident, he becomes more of a ruthless person.

After a few years, he's able to socialize, but not as much. Unfortunately, his dad dies in a traffic accident and his mom abandoned him in order to live with her lover shes been seeing. Haise is left broken emotionally, but doesn't want to give up just yet.

But then, a certain girl comes into his life, which causes Haise to relive his childhood trauma,
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or so he thought.....