In Asia's first such case, the plaintiffs claim South Korea's legally binding climate commitments are insufficient and unmet, violating their constitutionally guaranteed human rights.
A similar youth-led effort recently succeeded in the US state of Montana, while another is being heard at the European Higher Court.
The case -- known as "Woodpecker et al. v. South Korea" after the in-utero nickname of an embryo, now toddler, involved -- includes four petitions by children.
In 2021, South Korea made a legally binding commitment to reduce carbon emissions by 290 million tons by 2030 -- and to achieve net-zero carbon emissions by 2050.
To meet this goal, the country needs to reduce emissions by 5.4 percent every year from 2023 -- a target they have so far failed to meet.
If no changes are made, the plaintiffs argue, future generations will not only have to live in a degraded environment, but will also have to bear the burden of undertaking massive greenhouse gas reductions.
This, the case claims, would mean that the state has violated its duty to protect their fundamental rights.
Similar climate cases globally have found success, for example, in Germany in 2021, where climate targets were ruled insufficient and unconstitutional.
But a child-led suit in California over alleged government failures to curb pollution was thrown out in May.
The lawyer for one 12-year-old plaintiff told AFP that the age of the plaintiffs helped hammer home people's desperation for change, and urged the court to rule in their favour.
"This lawsuit is not just a symbolic lawsuit, but a lawsuit that we can and must win," Youn Se-jong said.
"The essence of the climate lawsuit is no different from the numerous constitutional issues related to fundamental rights that the Constitutional Court has judged, such as conscientious objection to military service or right to abortion," Youn said.
"If we delay our response to reduce the burden of climate change, that burden will be passed onto future generations."
