He pledged his allegiance to the country as a vow.

Kei is my best friend.

This lake is rich in diatoms.

He is in his unlucky year, so he needs to be particularly careful.

My signature is required on this contract.

He is traveling around the world in search of the elixir of life.

He needs long-term drug therapy.

His words reminded me of the proverb 'good advice may be uncomfortable to hear.'

The external urethral sphincter is an important muscle for controlling the excretion of urine.

This blade is very sharp.