This lake under the cliff wasn’t the destination of the twins’ hiking trip, they just stumbled onto it along the way.
“Come on, let’s jump down,” Rin got excited.
“I dunno, this looks dangerous,” Len shook his head.
“What’s the worst that can happen?” Rin laughed. “We miss the water and die?”
Without waiting for Len’s response she jumped right ahead.
“We miss the water and don’t die,” Len sighed, looking down at Rin’s broken body twisting in painful agony.
Still, Len knew she would die eventually if he just leaves her there, and so he continued his way unbothered.