(Pronounced in English "Heartful Boyfriend" - hato is a pun on pigeon or bird or something.)
It's Planet of the Apes, only with pigeons. You're the last human on Earth, and you're apparently going to a pigeon high school and getting caught up with the pigeon mafia (the Hawk faction vs the Dove faction) and at one point get eaten by Hannibal Lector pigeon.
Big discussion on it over at Quarter to Three.
Download here (blue text in the yellow box is the link), with the English patch necessary to read it if you're not Japanese here.