That the whole place is a shithole, and that Aki isn't the crazy one, the village elders and hierarchy are.
I figured you would say that, and while she's certainly the closest, I still disagree. Hibino isn't doing everything out of selflessness. She asked to go to the village, and the benefit is that she finally got to visit her mother's grave again. She also didn't go purely out of the desire to learn about her family's past, or to visit her mother's grave, or to protect Utao. We don't know the exact reason she gave her father (probably visit her mother's grave), but we found out a bit more from her walk in the forest with Moyako. Hibino didn't, "seem too put off by it." She wants to get closer to Kyouhei...really close. She's like an #FAFAFA.Except Hibino. To date she's pretty pure white.