Thirteen‑year‑old Sink Izumi is a born traveler, an enthusiast of sports, circus, and risk. Half English, half Japanese, the boy has circled many countries, trying everywhere to learn something new about acrobatics and the technique of handling pole weapons. The hero with the blood of "sea lords" is frankly bored in quiet Japan, where it is hard to let a wide‑minded soul flourish. Thus, on the spring holidays, despite the clear hints from his school friend Becky, Sink planned to go "historically" and train until exhaustion, preparing for the next tournaments. As is often the case, these plans were doomed to fail – after all, in an infinite universe there are plenty of places where strong, agile and reckless kids are always needed! In some world, on the vast continent of Froniard, many countries spread out, inhabited by beastmen capable of magic who solve international problems in the traditional way – war. Only war there, despite its obvious medievalness, is knightly and civilized. Yet even in such a war the Republic of Biscotti hopelessly loses to neighboring Galette, which breeds deep melancholy and gloom in society. To turn the situation around, young Princess Milhior F. Biscotti resorts to a last resort – summoning a hero from another world. These will be Sink"s holidays!