What would you do if you had a billion dollars? Witness Haru and Gaku as they enter the billionaire's club!.

Rud raids the treacherous labyrinths, uninterested in fabled riches but desperate to cure his sick sister. Kicked out by a conceited hero, Rud heads home empty-handed until he rescues a girl who exposes his unparalleled protection.

One fateful summer, a group of elementary school kids set adrift on an abandoned apartment building must look within themselves to find a way back home.