The current solar system is reaching it's end, and humanity is evacuating.
The trash/dumb/shitty Yukkuris don't listen to humans(as seem portrayed by this dosu telling others to take it easy), the guy in the 4th panel even asks if it's really okay to leave them and they respond it's ok.
Then all these oblivious manjuu rejoice as there are no more mister humans to bother them, and they wiggle their sorry asses in tears of joy to a bright new day without mister humans.
As the supernova turns the planet into glass they let out their last "Take it easy!".
EDIT: Here's the real summary from post #31250:
It's a non abuse story. It talks about a Dosu that lead yukkuris to multiply, then tries to restrain them resulting in its expulsion and leading to the destruction of the herd. It traveled over mountain, seas, deserts to build a herd it can be easy with but they all expel and then destroy it self (infighting or picking fights with humans, or starvation). The dosu repeated this for several hundreds of years until it realized it is special for living so long but it could never be easy. It settled down on an island and went to sleep for a thousand years.
Then it felt the presence of thousands of yukkuris and humans living on the marisa shaped island and it woke up finding both humans and yukkuri live easily. It lived on the island for 12000 years when the humans plan on building an artificial planet/star but have problems. The dosu realizing it possessed a lot of energy volunteered to make a star so the humans can anchor the planet. They name it the Marisa star system.
Ten billion years later, as a sun it thought back to the forest that raised her and its parents and siblings and other yukkuris. Finally as its core changes shape, which humans call super nova, it shouts out one last take it easy before imploding and traveling the universe as light.