Yakin Byoutou San

Yakin Byouyou San is the third mainline game of the Night Shift Nurses franchise, released on 2004 only on Japan. It has no relation with previous games of the series.

Sora is a perverted homeless man who has lost everything, to the point he even sold his family name. After disturbing a woman and her boyfriend in the middle of a public street, he is beaten to the point of near death and ends up on the gates of a hospital. He is found by a nurse called Yuu Yagami, who takes him inside the building, where he is nursed back to health.

He is then invited by the director of the hospital, Reika Mikage, in taking part of an experiment where he will take a drug for 30 days while living inside a closed facility inside the hospital. Sora quickly accepts in exchange of the vast quantity of money promised to him.

Yakin Byoutou San is a Simulation Game like previous game of the series: Sora chooses places where to spend his time and interact with the nurses working around the facility and fellow human subject Sakurakou Kujou, with dialogue choices raising affection points towards them. If he accumulates enough points of affection with them, an event occurs where the drug begins to give him genius-level intelligence, and he instinctively learns how to dodge the facility's safety system in order of doing things outside the view of the security cameras. Following the nurses around also unlocks events where he learns more about them.

And how Sora is a hopeless pervert with no good intentions in mind, he will use that knowledge to turn the beautiful nurses around him into his Sex Slaves.

Tropes used in Yakin Byoutou San include:

Beauty Mark: Shizune has a small mole near her mouth.
Blind Without'Em: Sora is able to trick Shizune in thinking he is Reika when her glasses are off.
Body Horror: Sora begins to suffer from horrible deformations from the drug in the last day.
Creepy Crossdresser: Sora wears like Reika in order of having sex with Shizune.
Girlish Pigtails: Yuu is very girly and has two big pigtails.
Girls Love Stuffed Animals: Hyori's room is filled with stuffed animals.
Gone Horribly Right: In Sakurako's ending, it turns out Reika giving her dogs intelligence equal to humans also made them regretful like humans and eventually not as loyal as dogs normally are; one of them eventually tells the press the whole story, leading to her arrest.
Hospital Hottie: All the nurses are beautiful and curvy.
Incest Is Relative: It's heavily implied Reika and Shizune, that are sisters, engage on such acts since Shizune doesn't mind having sex with Sora disguised as her sister.
Older Than They Look: Hiyori is her late teens, but acts and looks much like a child.
Ojou: Sakurako is said to be from a very wealthy family and shows disgust towards the protagonist specially because he is of a lower class.
Pet the Dog: In his "date" with Sakurako, Sora plays with toys alongside her like two innocent children. Sakurako actually feels grateful, saying she never had an experience like that when she was a child.
Princess Curls: Sakurako has two big ones in each side of her hair, and is he heiress of a very wealthy family.
Rapunzel Hair: Both Shizune and Sakurako have very long hair.
The Starscream: Shizune's route. She betrays her sister Reika for Sora because of her grown affection for him in her ending.
The Stoic: Shizune acts unfazed towards everything most of the time.
Talking Animal: Reika used the drug on her own animals, giving them not only intelligence but even the ability to speak.
Token Loli: Hiyori Kisaragi is on her late teens, but pretty much acts and looks like a little child.
Too Kinky to Torture: Hiyori doesn't care much about a dominatrix that Sora invited trying to torture her and quickly turns the table on the woman.
Two-Person Pool Party: One of the sex scenes with Yagami involves Sora and her having sex on the facility's pool.
Villain Protagonist: Sora is an unrepentant rapist who uses the intelligence given to him by the experimental drug as a mean to rape women.
You Have Outlived Your Usefulness: In the individual endings, Reika tells her animals to kill Sora once she has have already obtained the results she wanted from observing the effects of the drug on him.