He is majoring in the study of national law.

He understands the basic concepts of thermodynamics.

His father fell into a persistent vegetative state due to a traffic accident.

The National Research and Development Agency plays a crucial role in advancing science and technology.

She was a secret kunoichi (female ninja).

He threw a handful of sand into the sea.

"Once in a lifetime" means to cherish the encounter that happens only once in one's lifetime.

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

He was focused on his work all day long.

One day, he suddenly decided to go on a journey.