He started learning Ainu language.

I often play golf on weekends.

He was chosen to guard the president.

We go to the playhouse to watch a play on the weekends.

We spent the night in a mountain hut.

He mixed coffee and milk.

I like solving Tsumego problems.

We need to combine these data.

We have a responsibility to protect this world.

Ex post facto laws pose a problem for a fair legal system.