*Translated by Google Translate

　Introduction　

Climate change is destroying the foundations of society.
It is said that the global average temperature has already risen by 1.1°C compared to the pre-industrial era (around 1850-1900) due to the effects of greenhouse gases.

Extreme heat and torrential rains not only threaten lives and health, but also severely impact agriculture and fisheries, leading to soaring food prices and widespread anxiety about daily life. We are becoming a society where we cannot live without air conditioning, and the burden on living conditions and household finances is only increasing. This is not a problem that can be overcome by individual ingenuity alone. The effects of climate change will undoubtedly worsen further in the future.

However, Japan's climate change measures are not aligned with the globally shared 1.5°C target (see the case summary for details).

The government's failure to take necessary measures is destroying the peaceful lives of society as a whole.

▲Source) IPCC Sixth Assessment Report   twist

　Summary of the case　

This lawsuit will hold the Japanese government accountable for its inadequate climate change measures.

As you, the readers of this page, have likely noticed, the effects of climate change are becoming clearer year by year. Extreme heat, torrential rains, an increase in heatstroke cases, and crop failures—it is scientifically clear that these phenomena are caused by human activity, and countermeasures are needed all over the world. Japan is no exception, and the Japanese government, in particular, is required to take effective measures as soon as possible.

Climate change is a human rights issue, and the Japanese government has an obligation to take measures to ensure that human rights are not violated as a result of climate change. Furthermore, the Japanese government has an obligation to take measures to achieve the goal of limiting the rise in global average temperature to less than 1.5°C above pre-industrial levels (this goal is called the "1.5°C target") under international frameworks such as the Paris Agreement.

Specifically, the obligation is to reduce greenhouse gas emissions (gases such as carbon dioxide that cause the greenhouse effect) by 43% by 2030, 60% by 2035, and 69% by 2040 compared to 2019 levels. However, the numerical targets and policies set forth by the Japanese government do not align with these obligations.

Some may find it strange that climate change is being addressed in court rather than in the political arena. However, looking at the world, lawsuits are being filed all over the world, including in the United States, and especially since 2019, Supreme Courts and Constitutional Courts in countries such as the Netherlands, Germany, and South Korea have ruled that numerical targets that are not consistent with the 1.5-degree target are unconstitutional or illegal.

Furthermore, in July 2025, the International Court of Justice published an advisory opinion on the obligations of states regarding climate change, stating that all countries worldwide have an obligation to take measures to address climate change. Japan is included in this list of countries worldwide.

Thus, in addition to courts in various countries, international judicial bodies have also made rulings that take seriously the responsibility of nations regarding climate change. A major goal of this lawsuit is for Japan to achieve a groundbreaking ruling that follows in the footsteps of the rest of the world.

　Background　

Prior to the filing of the lawsuit, a total of 452 people from all over the country, who deeply felt the severity of climate change, came forward as plaintiffs.
The plaintiffs come from diverse backgrounds, including people whose lives were threatened by heatstroke, workers in primary industries such as agriculture and fishing, and children who will shape the future.
In addition to the plaintiffs, we have also received cooperation from many other individuals, including artists and celebrities, who have agreed to act as initiators and supporters.

The lawyers representing the plaintiffs gathered from all over the country. As this lawsuit is the first in Japan to question the legality of the government's climate change countermeasures, the entire legal team dedicated an enormous amount of time and effort to research, exchanging opinions, and preparing court documents, primarily the complaint.

Then, on December 18, 2025, we filed a lawsuit with the Tokyo District Court (first lawsuit).

Furthermore, on April 2, 2026, 454 additional plaintiffs filed a lawsuit with the Tokyo District Court (second lawsuit).

▲Scene from the press conference at the time of the first lawsuit filing

　Issues in the trial　

The two main issues in this lawsuit are ① and ②, but I will also explain the underlying obligations of the state as point ⓪.

⓪ Premise: National obligation

The Paris Agreement is an international legal framework (treaty) concerning climate change. Japan is also a signatory to the Paris Agreement. The Paris Agreement sets a target of 1.5 degrees Celsius, and the Japanese government has an obligation to reduce greenhouse gas emissions in order to achieve this target.

Furthermore, the Intergovernmental Panel on Climate Change (IPCC) is an authoritative intergovernmental body on climate change science. In its Sixth Assessment Report, published between 2021 and 2023, the IPCC reported that in order to achieve the 1.5°C target, greenhouse gas emissions worldwide need to be reduced by 43% by 2030 compared to 2019 levels, by 60% by 2035, and by 69% by 2040. These reduction targets have also been confirmed as necessary figures for emission reductions at the Paris Agreement Conference of the Parties, in which the Japanese government also participates.

In addition, international legal frameworks such as the Paris Agreement stipulate that developed countries bear heavier responsibilities than developing countries.

Based on the above, Japan is obligated to reduce greenhouse gas emissions by at least 43% by 2030, 60% by 2035, and 69% by 2040 compared to 2019 levels, in order to achieve the 1.5°C target.

① The illegality of setting reduction targets that are not consistent with the 1.5-degree target.

The latest reduction targets set by the Japanese government are outlined in the NDC (*) and the 7th Global Warming Countermeasures Plan, both formulated in February 2025. These targets aim for a 39% reduction by 2030, a 52% reduction by 2035, and a 67% reduction by 2040 compared to 2019 levels. In other words, Japan's reduction targets fall short of the figures set by the IPCC, and certainly do not fulfill its responsibilities as a developed country.

The first point of contention is whether the establishment of such NDCs (Nationally Determined Contributions) and climate change mitigation plans was illegal.

*This refers to the greenhouse gas reduction targets that signatory countries to the Paris Agreement submit and publish every five years.

② The illegality (unconstitutionality) of failing to enact effective legislation to achieve the 1.5-degree target.

As mentioned in point ⓪, the Japanese government has an obligation to reduce greenhouse gas emissions in order to achieve the 1.5°C target, and the same applies to the legislature. However, currently in Japan, there are no laws that set greenhouse gas reduction targets for 2030 or 2035, nor are there any legally binding emission standards.

The right to live peacefully in a stable climate without fear of harm to one's life, health, or property is a human right that should be guaranteed by the Constitution. The second point of contention is whether the lack of appropriate legislation to achieve the 1.5-degree target is unconstitutional, as it infringes upon the constitutionally guaranteed right to live peacefully.

　Social Significance　

The damage caused by climate change suffered by the 452 plaintiffs varies from person to person, but if things continue as they are, all of these damages will undoubtedly worsen in the future, and therefore, it is already difficult for any of the plaintiffs to live a peaceful life.

The effects of climate change are something that everyone, not just the plaintiffs in this lawsuit, has experienced. If this lawsuit determines that the government's climate change measures are insufficient, it will mark a turning point in Japan's climate change response.

Furthermore, if Japan's climate change targets and policies are aligned with the 1.5-degree target, it will at least reduce Japan's greenhouse gas emissions, which currently rank fifth in the world, and will significantly contribute to ensuring peaceful lives for everyone, not just the plaintiffs in this lawsuit.

Climate change is progressing at an alarming rate, and humanity has little time left to curb it. Beyond a certain point, human rights violations caused by climate change will escalate to infringements on more specific rights such as life, health, and property.

Through this lawsuit, we hope to make the government recognize that its climate change measures are insufficient, and to deter human rights violations against the plaintiffs and all other individuals.

　Use of funds　

• Public relations expenses (holding meetings, creating and maintaining a website, creating and distributing flyers and leaflets, etc.)
• Litigation fees (stamp duty, postage, printing costs, etc.)
• Transportation expenses, communication expenses, legal fees, administrative expenses, interpretation and translation fees, and other expenses (related to the lawsuit)

*If any money remains after the end of the project, it will be donated to an organization that engages in environmental protection activities, and the parties involved will not receive any profit.

　Plaintiff's thoughts　

Plaintiff: Kohei Saito (Associate Professor, Graduate School of the University of Tokyo) 

I filed this lawsuit because I strongly felt that climate change is no longer a "future problem," but is already threatening our lives and human rights. Extreme heat and torrential rains have become commonplace, and their effects weigh heavily on children, the elderly, and socially vulnerable people. Meanwhile, the responsibility for causing the climate crisis and the way in which people suffer the consequences are remarkably unequal. Despite this, the Japanese government's measures remain insufficient, both from a scientific and human rights perspective.

I felt that remaining silent in the face of this inaction would be an abdication of responsibility to future generations. A trial isn't a magic bullet that instantly changes society. Nevertheless, I believe there is meaning in citizens raising their voices and continuing to question the truth in the legal arena, and that's why I joined this lawsuit. Let's create a powerful movement together!

Plaintiff A (female) 

To be honest, I joined this lawsuit because I thought it would be interesting. I was excited because I figured I wouldn't get another chance in my life to participate as a plaintiff in such a major trial.

To my shame, until I joined this lawsuit, I had always viewed climate change and human rights issues as something that didn't concern me. Now, while supporting this movement, I want to choose my own lifestyle. Participating in this lawsuit has made me think about what I should choose and what I should not choose, given that I am dependent on the Earth to live.

There are realities that are hard to bear, but I want to focus on myself without comparing myself to others, be humble towards the planet, and cherish living each day to the fullest. And, if I'm lucky, it would be wonderful if my elementary school-aged son could think, "Mom, you're cool."

Plaintiff B (male, in his 20s) 

Internationally, there has been an increase in lawsuits and court rulings asserting that climate change is the responsibility of governments. Why are such lawsuits and rulings increasing? I believe one reason is the magnitude of the damage to future generations.
It's not just the current generation that suffers from climate change. Future generations, our children's generation, will also suffer (perhaps even more than we do). This lawsuit holds the government accountable, but at the same time, it should also be an opportunity for us to reconsider how we will pass on the problem of climate change to future generations, our own children.

Let's start taking action now so that we can proudly tell future generations that we have changed climate change.

▲December 18, 2025, at the Tokyo District Court

　Message from the assigned attorney　

Attorney Hayato Sekiguchi 

I was 13 years old in 2001, at the start of the 21st century. Even back then, I was familiar with the term "global warming" from social studies classes and television. In high school and college, I became interested in environmental issues and thought the 21st century would be the "century of the environment." In 2011, the Fukushima Daiichi nuclear disaster occurred, and I thought that renewable energy would become widespread like in other developed countries, but what Japan was doing was building new thermal power plants and exporting them. Japan, which adopted the Kyoto Protocol in 1997 and was at the forefront of the world in energy conservation and solar power projects, had before we knew it had become the world's fifth largest emitter of carbon dioxide in terms of national emissions and the fourth largest in per capita emissions, surpassing China.

For decades, Japan has let go of the opportunity to move in the right direction. Climate change is an event that will undoubtedly have a negative impact on social life, regardless of one's position, and will also be a source of that negative impact. Moreover, these effects will continue for generations to come and will only worsen.

We believe that our lives should not be solely about our own satisfaction. The meaning of our existence in this era lies in how we leave behind a rich global environment and Japan's four seasons for our children, grandchildren, and their grandchildren. With a firm resolve to ensure that we do not lose a sustainable planet in our generation, we intend to proceed with this lawsuit.

　Introduction of the legal team　

◼︎ Akihiro Shima, Tokyo Bar Association (Representative of the Legal Team, Chairman of JELF)
Rihito Yoshida

◼︎ Second Tokyo Bar Association: Nobuko Terada, Yu Adachi, Asa Kanda

◼︎Aichi Prefectural Bar Association: Yusuke Nakane, Rin Fukuda

◼︎Shiga Bar Association, Hayato Sekiguchi

◼︎Kazuhiro Kasahara, Fukui Bar Association

　In conclusion　

Climate change is not a distant future issue. We already feel its effects in our daily lives: days too hot to go outside, rising food and electricity prices, and anxieties about heavy rains and natural disasters.

This lawsuit is not meant to end with a simple "it can't be helped," but rather to challenge the legal system to question whether current climate action is truly sufficient. We want to create a society where future generations won't be asked, "Why didn't you do anything?"

However, continuing this trial requires a great deal of preparation and specialized work, and support is absolutely essential. If you can sympathize with our situation even a little, we would be grateful for any support you can offer in any way that is convenient for you.

Even small steps, when combined, can become a great force. Your support will help spread this voice throughout society. We would greatly appreciate your support.

*Please also see the following website for more information on climate justice lawsuits.