He decided to descend from the mountain because he got altitude sickness.

This world where people live is beautiful, and sometimes harsh.

Humans can make mistakes.

This old document details the lifestyle of humans.

Anthropozoonosis, or animal-derived infectious diseases, have the potential to spread between humans and animals.

He chose that method against his will.

This tree is very hard.

He is a person with a strong heart.

He finished the job in slightly more than an hour.

Tsuyoshi is my best friend.