I think his Japanese has improved quite a bit, hasn't it?

I am busy with work during the daytime.

My keys are inside the house.

I was wide-eyed watching his amazing performance.

He is a new member of our team.

He is a member of that company.

He is an important employee of that company.

The security team is guarding the bank all night.

He chose a life as a home security guard, meaning he chose to be a recluse.

The sentry dog is watching over the factory all night.