During a high school student's lunch break, Yuzo Ogata and his friends are unexpectedly whisked away to a realm of swords and sorcery by the Princess of Space-Time Magician. Tasked with defeating the Demon Lord as destined heroes, they are startled by the princess's revelation that they were not the only ones summoned. Amid the initially relaxed atmosphere, a shocking truth emerges – an extra hero has been mistakenly brought from their world. Now, as this accidental hero grapples with his newfound role, his future in this mysterious world hangs in the balance.