He enlisted in the army as an infantryman.

I have been to the Northern Sea.

Hormones play an important role in the body of living organisms.

He ran as fast as a galloping horse.

Mr. Ootsutsu is my best friend.

He gave me that important information.

He informed me of the party schedule.

He is serious about wanting to learn Japanese.

He once participated in a war as an infantryman.

He did something foolish.