our captain, protagonist, knight in shining armour, our hero named Hiro is a boy that leaves in a rural area in the country of Reubai, his father kai Yates is a former popular and well sought out for labyrinth explorer that retired at the age of 39 after he married Hiro's mother carmella Yates who is a normal housewife that used to be a regular explorer (info on how they met and fell in love will be given on vol. 1)
anyway...Hiro hasn't used any of the crystals that are extracted from the labyrinth to modify anything in his body and wanted to train his body and get stronger naturally with exploration and thanks to that while he isn't the most strongest or fastest (being agile is his best trait) he is still somewhat comparable to the people who use crystal and significantly stronger than the people who are poor to afford them
Hiro loves to explore the cave besides a beach to the point that he always to visits it to spend some alone time there, but one day at the age of 14 while exploring he found something that will change his life forever