In a world where humans once thrived beneath the ocean's surface, a divide emerges when some choose life above the water, losing their underwater breathing gift, 'Ena.' Amidst this split, 'Nagi no Asu kara' unfolds the tale of Hikari Sakishima, Manaka Mukaido, Chisaki Hiradaira, and Kaname Isaki. These childhood friends face a new reality attending a surface school, where they meet Tsumugu Kihara, a sea-loving student. As they navigate the animosity between sea and surface dwellers, personal turmoil, and an imminent catastrophe, Hikari and his companions brace for transformative challenges.