Grave of the Fireflies
A harrowing WWII tragedy of two orphaned siblings; widely held to be one of the most devastating films ever animated, full stop.

Overview
Grave of the Fireflies is the Studio Ghibli film people recommend in hushed tones, usually with the expression of someone handing over a small emotional explosive. Directed by Isao Takahata and based on Akiyuki Nosaka's semi-autobiographical story, it follows siblings Seita and Setsuko trying to survive in Japan during the closing months of the Second World War.
It is not a war adventure. It is not an uplifting tale of resilience dressed in ration-paper sentiment. It is a tragedy about children, pride, hunger, social failure and the merciless arithmetic of a collapsing home front.
Why it matters
The film matters because it is one of animation's clearest refutations of the idea that the medium belongs only to fantasy or childhood comfort. Takahata uses animation not to soften suffering but to make memory precise. A tin of sweets, a firefly, a shelter, a small gesture of care: each becomes unbearable because the film knows exactly how ordinary catastrophe can look.
It also sits as a crucial counterweight inside Ghibli's reputation. This is the studio of Totoro, yes, but also this: a film about children abandoned by history and by adults too compromised, frightened or depleted to save them.
What to expect
Expect a devastating watch. The film is not graphic in the usual modern sense, but its emotional violence is severe. Content includes wartime bombing, starvation, child death, grief, neglect and social collapse.
It should not be sold as a casual "must-see" without warning. It is a great film, but greatness is not the same as comfort. Some viewers may only need to see it once. That is not a criticism; it is a perfectly reasonable act of self-preservation.
Adaptations and versions
Grave of the Fireflies is a theatrical film directed by Isao Takahata, adapted from Akiyuki Nosaka's story. It has an unusually distinct place in the Ghibli catalogue and has had different rights and availability patterns from some other studio titles, so publication details should be checked.
The film stands alone. No broader Ghibli or anime context is required, only emotional readiness.
Where to start
Do not make this someone's first Ghibli film unless you know exactly what they are asking for. It is essential, but it is not introductory in the warm sense.
Watch it when you are prepared for a serious war tragedy and can give it proper attention. Background viewing would be borderline indecent.
Verdict The SFcrowsnest take
Grave of the Fireflies is a masterpiece, and also a wound. Takahata does not weaponise sentiment; he simply shows children losing a war they never started. Approach with respect, tissues and no expectation of being put back together afterwards.