The 63-year-old rallied over 450 plaintiffs across Japan last month in a landmark lawsuit seeking damages from the central government over its alleged "grossly inadequate" response to climate change.

For Shima, the suit is "the culmination of everything" he has spent years fighting for, first as a musician and then a lawyer.

When the punk movement barrelled through Japan in the late 1970s, then-teenaged Shima was convinced he would "change society through rock-n-roll", he told AFP.

Decades later, he has lost none of his fervour.

Roaring the lyrics "Free Palestine!" and "Dance in the street for your rights" at a tiny, dimly-lit Tokyo bar in December Shima lauded his latest legal battle between songs.

"There are people spewing carbon dioxide because of their selfish lifestyles, while people who don't live like this at all are seeing their islands on the verge of sinking," he told audience members during the December performance.

"Our future generations will be the biggest victim," he said, eliciting a few nods.

- 'Superbly cool' -

A longtime fan of Shima, 60-year-old caregiver Kumiko Aoki was among those inspired to join the lawsuit as a plaintiff.

"The fact that he peppers his songs with clear messages like 'no war'... I think that's superbly cool," she told AFP at the bar.

Aoki and her fellow plaintiffs argue that Japan's "unconstitutional" inaction on climate change violates their constitutional rights to health and a peaceful life, and criticise Tokyo's emissions reduction targets as unambitious.

Japan is committed to cutting greenhouse gas emissions by 60 percent by 2035 and 73 percent by 2040 compared with 2013 levels -- reaching net-zero by mid-century.

Experts say the suit's chances of winning are slim, but it could raise awareness and stir public opinion.

For Shima, the suit is the endpoint of a journey that began as a teenager, when he read the Japanese novel "Compound Pollution" -- a diatribe against industrial waste, agricultural chemicals and food additives.

Shima explained that as a teen poring over the novel he'd thought: "As long as we remain hell-bent on pursuing materialism and an economic status, our planet won't hold up."

He became a household "radical", chivvying his parents into replacing laundry detergents with bar soap and boycotting their car and got involved in other causes, from poverty to discrimination.

- Nude shoot -

For many years, music was his medium, and he embraced punk's anti-establishment message enthusiastically.

He and his musician friends even shot a CD cover nude in front of Japan's parliament as a political protest.

But as Shima turned 41, "it dawned on me that all my talk about social revolution or my niche band activity wasn't changing society a bit".

He went back to school and became a lawyer in 2010, with his first lawsuit naming a polar bear as a plaintiff and arguing global warming amounts to pollution.

After the 2011 Fukushima nuclear disaster, he led a lawsuit against major nuclear reactor suppliers and also formed a new band: "Shima Kick Jiro & No Nukes Rights."

Given his age, he acknowledges his latest lawsuit might be his last, but believes it addresses profound questions about the future.

"We intend for this lawsuit to prompt the question of what kind of society we want to live in 30 years from now," he said.

For all his environmental passion, Shima admits he hasn't made songs about climate change yet.

"I haven't been able to find a way to make words like 'climate' sound cool," he said.

Could his landmark lawsuit change that?

"I will try," he said with a smile.