Before he transfers into Ataraxia, the marine-float academy built to fight off invaders from another dimension, Kizuna Hida is a nobody: his HHG output barely registers next to his classmates'. His older sister pulls the strings to get him in anyway, and pilot Aine Chidorigafuchi's unit soon learns why: the girls' Heart Hybrid Gear only works at full strength through direct physical contact with Kizuna. This original light novel lays out the premise and cast that the manga and anime later adapt.