Currently available as a novel and manga! A story featuring a super-strong heroine with a tofu-like mentality and a protagonist with a strong mind and strategic thinking! In 2045 AD, Earth was simultaneously invaded by four parallel worlds. Explorers, consisting of two men and two women from each country, were selected to prevent the invasion by conquering dungeons created by each parallel world. The borders of each country were sealed off by an impenetrable barrier, making trade and electronic communication impossible. The only resource that can save the countries from the brink of destruction is the magic stones obtained by the explorers during their dungeon conquests. The protagonist, a regular college student, is chosen as one of Japan's explorers. With Japan's borders sealed and trade cut off, the country faces a crisis. The magic stones obtained from the dungeons become a vital resource for aiding Japan, and the young man finds himself not only fighting for his life but also for the fate of his nation. The entire nation watches as the young man, under the watchful eyes of the Japanese people, advances through the dungeons, which serve as the stage for this war. His enemies include powerful monsters, magic-wielding sub-humans, wild angels, and cool robots. When the young man meets his female partner, Japan's rapid advance begins! A heartwarming and light-hearted comedy filled with love and lovable characters!