Private Nurse

Since childhood, Hiroki has suffered from a malady that leaves him weak and tired. Ayano, his neighbor and childhood friend, has always taken care of him as best she can. Even with her care and attention, he can't help but fall into a depression that he will never get better, since it seems most days all he can manage to do is get to school and back home again. Then one day there is a knock at his door. When he answers, a pretty young girl wearing a nurse's outfit gently says, "Hi, I'm Maria. I am your private nurse." Meanwhile, the new school nurse, Mio, also takes on the task of curing Hiroki. Ayano must overcome her jealousy that these two women have intruded on her relationship with Hiroki while at the same time hoping that he can be cured. Mio wants to cure him to prove she can be a better nurse than her school career implied. Maria is confident that she can cure Hiroki, but she can only stay with him for 30 days, and may be more than what she seems.

Private Nurse is a Visual Novel-style Eroge from Angel Smile. While it does have some amount of sex in it, it is entirely incidental to how the story unfolds. And the story is nothing short of fantastic. In its most basic form, it's a love story, but it calls out to several other styles as well. There is a small amount of the fantastic implied, but overall it is a story about four ordinary people. Even though the story does play to a lot of tropes, as you can see in the list, it also has a tendency to twist, subvert or invert them at some point, which can keep the story from feeling too cliched, and more realistic. Depending on the decisions you make during the game, the good endings vary from a truly Crowning Moment of Heartwarming to a nearly tragic Bittersweet Ending. Expect many Tear Jerker moments in between as the three women do their best to try to cure both Hiroki's body and spirit so he can look forward to having a normal life.

For some reason Private Nurse never seemed to get much wide-spread notice as similar games such as Kana: Little Sister or Yume Miru Kusuri despite having many common elements.

Tropes used in Private Nurse include:

Anchored Ship -- Hiroki and Ayano were officially dating when they were younger, but Hiroki called it off because he didn't think it was fair to saddle her with his illness. She never quite forgives him for not considering her feelings but still remains entirely devoted to him. If you pick Ayano's storyline, they get better. If you pick a different storyline ... it can get worse.
Angst -- Sort of? There are implications that Hiroki's sickness is at least as much psychosomatic as physiological and that he needs to be convinced that he can get better if he doesn't give up on himself.
Bittersweet Ending -- Maria's ending. And how. And this is considered a good ending.
But Now I Must Go -- Maria says she can only stay with Hiroki for 30 days. You can choose to try to get her to stay at the end, but I don't recommend it.
Childhood Marriage Promise -- Not exactly, but Ayano and Hiroki have been friends since they were both children (and even officially dated for a while) and she has said she will always take care of him.
Crowning Moment of Heartwarming -- Ayano's ending is just full of yay.
Eroge
Healing Hands and Intimate Healing -- Maria.
Hentai -- Almost entirely incidental to the plot.
H-Game POV Character -- Hiroki is probably a Type IIB - generally a nice guy, but depressed and moody because of his illness.
Ill Girl -- Inverted; Hiroki is the one who's sick.
Magical Girl -- Maria. Maybe. It's left very ambiguous.
Mood Whiplash / Misaimed Marketing -- If you find the English-translated version of this game for sale, the ad will invariably focus on the point of it being a hentai game.
Porn with Plot -- HEAVY on the plot.
Token Loli -- Yuno, Ayano's little sister. For an Eroge game the expected is completely avoided -- she is not an end-game storyline, she's just Ayano's cute little sister.
Tsundere -- Mio first sees Hiroki as a good project to redeem her awful med school grades, but soon becomes fond of him and genuinely wants him to get better.
Unwanted Harem -- Only technically. There are three girls, but there is never much real competition between them. Although in some endings, the "Unwanted" part gets taken very seriously.
Utsuge -- Clearly.
Victorious Childhood Friend -- Ayano if you pick her path.
Visual Novel