The tough base of this mushroom is very hard.

He is the champion of the stone, paper, scissors game.

We need mutual understanding.

He believes in 'an apple a day keeps the doctor away', so he eats fruit every day.

Research on xenotransplantation has the potential to open new frontiers in medicine.

This river has a lot of small stones.

This rock is a type called nepheline.

Ishimoto is my best friend.

Ishihara is my best friend.

Ishiwara-san is my best friend.