He is an expert in ring theory and has written many papers in the field.

The duct design of this building is very complex.

We need to make a plan for the new coronavirus.

Taisaku is my best friend.

We plan to enjoy camping out in the mountains this weekend.

We decided to camp out in the mountains.

That man is my father.

He was projecting an image onto the wall.

He became friends with the natives of that area.

This mansion is known for its rare architectural style.