L: Change the World

SPOILER ALERT! This page contains unmarked spoilers.

After defeating Light by writing his own name in the previous Death Note film, L has 23 days left to live. They restlessly pass away as he tries to solve as many cases as possible, until he receives a phone call from a young boy in Thailand, the only survivor of a lethal virus and formerly under the care of F. At the same time, a girl named Maki watches her father inject himself with the virus under threat from a bio-terrorist group, Blue Ship, who want to wipe out humanity. She escapes and finds L, but when Blue Ship arrives she too injects herself in order to get Revenge on the group. To her surprise, the virus is completely dormant, and she, L and the unnamed boy go on the run trying to find someone to recreate the antidote from the young boy before the virus becomes active and L runs out of time.

Once the antidote is almost complete, Maki again attempts to get her Revenge and leaves to infect K, the ringleader, but is caught and put on a flight to America. As the passengers and terrorists alike begin to succumb to the virus, L, with the help of an FBI Agent, Hideaki Suruga, boards the plane and delivers the antidote. Maki ultimately chooses to give up on revenge and is left in the care of Suruga. The next day L drops off the boy at Wammy's House and gives him the name Near. Having reached his last day, he admits he wishes to live longer, and quietly goes off to die on his own.

There's also a light novelization

Tropes used in L: Change the World include:

Big Heroic Run: L attempts one when he realizes Maki's gone, but is too late to find her.
Body Horror: Maki's dad injecting himself with the virus, while simultaneously being burned to death by K. Maki's probably going to be dreaming of that for a good long while.
Carrying the Antidote: Blue Ship are rendered unable to use the virus near the beginning when the antidote is destroyed and therefore if they released it they too would die. Though in the end, the leader releases it anyway because (unbeknownst to their henchmen) they are willing to die for their cause
Child Prodigy: Near, who is a math genius and solves Maki's homework for her.
Children Raise You: Maki and Near do this for L.
Death Is Dramatic: Dying from the virus certainly is.
Depopulation Bomb: The point of the virus. Blue Ship wants an antidote handy so that they can get rid of most of the world's population but not themselves, naturally.
Friend to All Children: Despite having no people skills, L quickly forms a bond with both his young charges.
Heel Face Turn: While not evil, the only reason Suruga is helping is to gain L's trust in order to get the Death Note for the US government. When L reveals he burned them, Suruga decides to help him anyways, proving L's trust well-placed.
The Hero Dies: L, of course.
- Foregone Conclusion: Assuming you've already seen the other two Death Note movies.
Hero Stole My Bike: After being caught on the train, L, Maki and Near have no choice but to avoid public transport. In the next scene they are cycling away on bikes that are clearly not theirs.
Hoist by His Own Petard: Subverted in that K is perfectly willing to die from the virus so long as it achieves her goal of ridding the world of humanity. L doesn't let her.
- K, at least, is willing to die from the virus. Matoba? Not so much.
Innocence Lost: Maki watches her father kill himself violently in defiance of the terrorists' threats. This prompts her to want to murder them in revenge.
Like You Were Dying: L puts up his best front for Maki and Near, even holding a picnic together while in hiding.
Living on Borrowed Time: L gives himself 23 days to live in order to beat Light, but his death is sealed from the moment he writes his name down.
My Death Is Just the Beginning: The aversion of this is a driving plot point. The ecoterrorist Big Bad has a super-virus that will wipe out humanity, but he is not willing to die along with the rest of us. However, the scientist who created a vaccine destroys it and kills himself after learning of the villain's plan rather than let the plan succeed, causing the villain to go after the scientist's daughter, who has notes on the vaccine and who L takes in.
Mythology Gag: Near, an Alternate Continuity version of the manga Near.
- The Stinger has L eating a chocolate bar a la Mello.
The Plague: The virus that was created is a mix of ebola and influenza, highly contagious, and quick to mutate. Naturally finding a cure before it wipes everybody out is the main plot of the movie.
Papa Wolf: L.
Peaceful in Death: L writes that he will die quietly of a heart attack, standing in contrast to Light's Undignified Death.
Race Against Time: In a twist, it is the heroes' unfortunate actions that are time sensitive. Maki is the one who injected herself with the virus to begin with, and it has to be cured before it becomes active or she could kill innocent bystanders. L likewise is at the last of his days having written his own name in the notebook and has to get the problem solved before he dies.
Red Right Hand: One of the principle terrorists has a cloudy blue left eye.
Sliding Scale of Cynicism Versus Idealism: Surprisingly falls well on the side of idealism. No matter how horrible the actions of Blue Ship are, humanity's capacity to solve its own problems and choose healing over revenge wins out in the end.
So What Do We Do Now?: With Watari dead, the Kira case solved, and only 23 days left to live, L falls into this, trying to pass the days solving as many cases as possible despite his despondence. After the Blue Ship case is over, he realizes he did want to keep on living.
Spotlight-Stealing Title: The first and second movie adaptations of the franchise are Death Note and Death Note: The Last Name. L: Change the World is the third in the series.
Synthetic Plague: Blue Ship manufactures the virus in order to wipe out humanity and restore balance in the ecosystem.
Undignified Death: Ryuk tries to stop L from burning the Death Notes, telling him he will die anyways, and reminding him that Light thought he could become a god with them. L asks whether Light died like a god, and burns them without regret.
- Dying from the disease definitely counts.
Wanted Poster: K goes on TV and declares Maki to be a medical patient with a deadly virus who must be detained at all costs. This, along with the posters plastered everywhere, makes it very difficult for the group to move, especially since K is an acclaimed scientist, so no one doubts the story.