One Piece: Don't Worry, I'm a Doctor - Chapter 55 - : Too Timid!

'Confucius spoke not of the bizarre, the valiant, the rebellious, nor of spirits and demons.'This is the story of Mok Gyeongwoon, AKA the First Heavenly Demon - Cheon Ma, the forefather of the main character of the popular novel and manwha Nano Machine. This story is the prequel to Nano Machine, taking place 800 years earlier.

Oosuki Masato is an ordinary high school boy who is magically transported to an alternative world, but for some reason his doting, over-protective mother comes along as well.

The so-called 『Enjoy the Human Lives Show Humans Sent to Another World With a Cheat』was trending amongst the Gods. Kanbara Kanata, one of the chosen humans ended up incurring the Evil God’s wrath and as a result, was sent to the worst dungeon,《Cocytus》. But, in a place where he was supposed to lose his life, he met Lunaère, a self-proclaimed misanthropic immortal girl. He was saved by her, who then decided to train him ’till he could at least protect himself.「Master, I think… I’ve become strong enough.」「It’s Not enough! Erm, outside of this dungeon is a dangerous place you know!」「Seriously!? More dangerous than this place…」This is the story of Kanata who was trained by his master, who easily succumbed to loneliness, till he became the greatest hero of legend, and yet was unaware of it.

What would you say is the most valuable thing in this world?