Narcissu

This is the story
of a girl whose heart was standing still
and a boy whose breath was being stolen away,
both of whom die.

Narcissu is a freeware doujin Visual Novel by Tomo Kataoka, former head writer of Nekonekosoft and officially translated by insani (at least for the first game). Even though the original company he worked on produced Hentai visual novels, this piece is clean.

The protagonist, suffering from a terminal disease (identified by the official English site as lung carcinoma), was moved into hospice in the 7th floor of a hospital, where he will be cured, supposedly. Until he met Setsumi, a girl also suffering from an unknown terminal disease, who told him otherwise: this is the place where you are left to live and die. It's the prison. You either die there or at home, no exceptions. He started to talk to her, and with that, he thinks that both him and her don't want to die either there or at home. Driven by the pictures of Narcissus, they decided to steal the protagonist's parent's car and escape, to Awaji Island, to see the flowers...

There is also a prequel called Narcissu -side 2nd- set about six to seven years before Narcissu, which tells the story of Himeko, a cheerful and Genki Girl and a former 7th floor helper who unexpectedly be a patient at the same floor she volunteered to help. Set in a summer day, when Setsumi, currently a regular outpatient of the hospital, went for regular check-up, meets Himeko, and their story begins there. The English translation for this ~~is currently in the Vaporware state~~ is finally out.

A third game, Narcissu 3rd -Die Dritte Welt-, is a compilation of several stories set in the same world. Unlike previous works in the series (disregarding prior released any supplementary material), it is a commercial release.

An omnibus edition of all three games, Narcissu -moshimo ashita ga aru nara-, has been released for the PSP.

The first game is available here. The second game ('bundled' together with the first) is available here.

Tropes used in Narcissu include:

April Fools' Day: The English version of Narcissu -side 2nd- was allegedly planned to be released on this day, but was instead uploaded a few hours before. Regardless, it took a few moments for some people who caught wind of it to realize it wasn't a joke.
Author Appeal: Cars
Author Tract: The author's view on medical care system, maybe (this is speculation on part of the translator).
Bittersweet Ending: Please refer to Let Them Die Happy.
Chekhov's Gun: Related with the Foregone Conclusion. The first novel begins by giving us the suicide statistics on Japan. You don't understand what to do with that information until the end, just before those statistics are repeated again...
Crazy Prepared: Setsumi.
Cutesy Dwarf: Setsumi is noted for her childlike appearance, and Yuka can be seen as one too (see Man Child below). Chihiro may also qualify. Himeko is a tiny girl too in the illustrations, but for some reason no one mentions it directly in the novel.
Determinator: The protagonist, while suffering lack of medication and fatigue, is able to drive the car for a whole week with only small rest and not so healthy diet.
- Though according to one of the translators, this may just be a case of the author taking some creative liberties as to what a person with untreated terminal lung cancer is able to accomplish. See below.
Did Not Do the Research / Shown Their Work: The translator, being medical student, has stated that there are several inconsistencies of the medical system in the story with real life, but at least he get several parts right.
Driven to Suicide: Setsumi. Foreshadowed by the statistics on suicide who are the very first text we see.
Emotionless Girl: Setsumi. She starts to open up along the way, though. Given that she was virtually forgotten by her friends, it makes sense for her to become this.
Fan Translation: Officially acknowledged by the maker.
Foregone Conclusion: Read the quote. Partially subverted in the first game, where Setsumi dies, but not the protagonist. The latter's death is instead implied to be near in the second game's hidden epilogue sequence that takes place nearly half a year after the first as he passes his "rules" onto Chihiro, which she took heart.
Four Is Death: A common mantra among those who inhabit the seventh floor is that no one returns a fourth time.
Freudian Trio: In Side 2nd: Himeko (Id), Chihiro (Superego), and Setsumi (Ego).
Genki Girl: Himeko
Go Out with a Smile: Setsumi.
Hey, It's That Voice!: Side 2nd stars Yūko Gotō, Natsumi Yanase, and Mamiko Noto.
Ill People: All protagonists and heroines will become this.
The Ishmael: The protagonist, arguably.
Japanese Christians: Chihiro and Himeko are Catholic, though Himeko claims to be only a "fake Catholic"; her struggle to resolve her crisis of faith before she dies is a major part of her storyline.
Jerkass Facade: Himeko towards Chihiro, not wanting her to feel sad after she passes away, and not wanting to be treated pitifully by her.
Let Them Die Happy: Both the protagonist and Setsumi discovers several things along the way, and both of them will die with happy memories that they share.
Light Novel: A light novel adaption was written by the original author with its story modified to incorporate elements from Narcissu 2.
Man Child: Yuka.
Morality Pet: The girl in Himeko's flashback. Her sudden change of behavior caused Himeko to turn cynical and abandon her faith in God as a Roman Catholic. Himeko spends time with Setsumi to relive her days as a hospice nurse with the girl.
My Greatest Failure: Himeko unable to advise the girl she is in charge with to stop starving to death, after the girl learns that her parents abandoned her and she would eventually die. This event causes Himeko to stop believing in God.
No Name Given: The girl in Himeko's flashback. The protagonist's name is never given in the first two games, but is revealed to be Yu Atou in various supplementary works, such as the light novel and manga adaptions.
Older Than They Look: Setsumi looks like a teenager, but she's 22. Possibly justified by her illness, if it's the kind that stunts her development, but the game isn't clear about what, exactly, she suffers from.
Parental Abandonment: The girl's parents abandoned her for her terminal illness, which she doesn't even know
Rage Against the Heavens: Himeko, the final item in the list of 10 things to do before she dies.
Rapunzel Hair: Himeko is depicted with very long hair in the illustrations, though it's never mentioned in the text.
Road Movie
Romantic Two-Girl Friendship: Setsumi and Himeko. You know it's true.
Shout-Out: There's a small one in the second game, where in one scene Himeko remarked that she doesn't take it kindly to be overtaken by a Levin.
- It is, in part, a translator thing since in the voice-over Himeko only stated that the car passing her is a "Hachiroku", and neither the original text or the translated text make any description of the headlights that could be used to identify the variant. A well-informed fan, of course, knows that a Toyota AE-86 comes in two forms, both available as a 2-door notchback coupe or a 3-door hatchback: the Corolla Levin (as the text said), and the more famous Sprinter Trueno. The translators made it a bit more funny, since there are actually two Levins in Initial D: the AE86 Levin owned by Wataru Akiyama, and the AE85 Levin owned by Itsuki Takeuchi.
Soap Opera Disease: The first game and prequel have a total of four terminally ill characters; not one of their ailments is ever specified, although one of the translators has done some speculation. At any rate, none of them seems to be sick enough to prevent them from traveling all over the country and subsisting on junk food.
Something Completely Different: In the third game, one of the stories takes place in medieval Europe and stars a swordfighting princess. No, seriously. Incidentally, it's the only one of the game's four stories written by Tomo Kataoka himself.
There Are No Therapists: No mention is ever made of clinical psychologists or psychiatrists on the 7th floor hospice despite how hospice inpatients are known for starving themselves to death; it's in the "rules". This may be justified by the relatively low numbers of such people in the Japanese health system and the cultural stigma against seeking psychiatric help.
- That said, it's fairly common in Real Life for terminal patients to intentionally starve (or more commonly, dehydrate) themselves in order to hasten death, even in places where physician-assisted suicide is legal. Some end-of-life care professionals even recommend it outright.
Utsuge: Many have admitted to crying over the original game. However, this is a unique case, as this was not the intentional on the part of Kataoka; according to his notes for the second game, he was surprised that so many have reacted in such away. As such, in side 2nd, he attempted to downplay the deteriorating health and death of the characters in order to have his messages and themes stand out more over the "tear-jerker" elements that would have his audience empathize with the characters.
Vaporware: The English translation of Side 2nd has quite a history behind it, as a combination of lack of time due to work for one translator and the complete disappearance of the other delayed the game past its scheduled release. It is slightly infamous for taking nearly three years to complete since its announcement.
Vitriolic Best Buds: Himeko and Yuka.
You Didn't Ask: Setsumi has an envelope full of money the entire time, and doesn't tell the protagonist about it because, well, he never asked. Of course, by the time she reveals this, he'd already stolen clothes from a laundromat, attempted to rob a pachinko parlor, and was about to speed away from a gas station without paying, all because he thought they were broke. Real thoughtful of her.