Sakujitsu

In this world, people actually drove themselves underground, literally, not metaphorically, living in colonies carved out of rock, with the surface world long forgotten. That's the world Memempu and her dad Gagumber are stuck in, and it's a strange setup that pulls you in almost immediately. Memempu is nine years old and genuinely brilliant, the kind of kid who's already figured out what she wants: to become a Marker, one of the explorers who chart the vast underground labyrinth beneath their colony. Her reason is personal: her mother disappeared into that labyrinth, and she intends to find her. Gagumber used to be a Marker himself, which is exactly why he wants nothing to do with this plan. The labyrinth is full of kaiju, it's unmapped and dangerous, and he's seen what it does to people. They go anyway. The dynamic between these two carries the whole thing: a reluctant, scarred father and a daughter who's too smart and too stubborn to be talked out of anything. If you liked Made in Abyss for its underground world-building, or Gurren Lagann for its father-figure-and-kid energy, this scratches a similar itch with a warmer tone. It's not trying to traumatize you. The humor is light, the relationship feels real, and the world has enough mystery to keep you curious about what's actually down there.