The dragon in Dra Koi falls in love with the protagonist after he hits the reverse scale on her neck, after which she follows him around blowing stuff up until he agrees to date her.
In Deiz, the player character is one of these towards the director Iris, to the point that he knows when she will walk by above his classroom.
Miho from Liar Liar was being stalked by Wakabayashi for a while. She feared for her life but the police couldn't do anything until he physically harrassed her, the adults at school didn't believe her, and everyone insisted she was in the wrong for not giving Wakabayashi a chance. She almost hit a Despair Event Horizon but decided to kill him, though she couldn't get herself to do it so she got Yukari to do so. This event was her Start of Darkness.
Hibiki from Lux-Pain is this towardAtsuki but is mainly played for laughs because of the situation that makes him seem like one mainly getting Atsuki's number because Atsuki isn't going to give him his number anytime soon and Ryo doesn't have a cellphone in order to give Hibiki Atsuki's number.
Monika is revealed to be one for the player. Not the character you're playing as, the player. All the Surprise Creepy elements are from her tampering with the game so that she's the best romantic option. She edits the other girls' files so their worst traits are exaggerated, leading to two killing themselves out of Sanity Slippage. When that doesn't work, she deletes them from the game entirely. She also has a habit of railroading options in her favor, such as making the cursor move towards her name when the player is selecting who to help out with festival preparations in Act 2. By the time of Act 3, Monika is the only girl present in a heavily glitched game, who talks openly about her love for the player.
Yuri devolves into one in Act 2, as a result of the aforementioned Mind Rape. When she's first introduced, she comes off as a sweet Shrinking Violet who has some darker interests but is otherwise harmless. However, Monika tampers with her, making her increasingly more clingy and unstable while obsessing over the player character. While in Act 1 Yuri was simply the type who'd buy two copies of the same book so that she'd give the player character one in an attempt to impress him, in Act 2 she tries to push the other girls away from him, makes creepy and often perverted comments, and even steals things from him. At the height of her Sanity Slippage, she confesses her love in a crazed manner, only to stab herself to death regardless of the answer. Monika even references the Yandere trope by name when talking about her in Act 3, despite ironically driving Yuri to that state out of a desire to get closer to the player.
In one of the endings Sayori also begins going down the same route as Monika: being meta-aware and desiring to have the player all to herself. It's suggested that whoever gets the Club President role gains meta-awareness, which leads them to do irrational things once they know the truth. Fortunately, Monika post-Heel Realization intervenes, blocking Sayori's attempts to take over the game the same way she did. If you get the Golden Ending, however, this plays out differently: Sayori will again reveal that she's become aware of the player, but will actually thank them for going for 100% Completion by trying to get as many CGs as possible through Save Scumming: all she wanted deep down was for everyone to be happy, so she was impressed that you'd go to such lengths.