He missed a once-in-a-lifetime opportunity.

I couldn't get in touch with her for a week.

We will meet again in one month.

Sanichi is my best friend.

There was not a speck of dirt on his shirt.

He has a pencil.

He tried to solve the problem all night.

He solved the problem solely by himself.

Hitori is my best friend, she always helps me.

Hitori is my best friend.