"It was a hospital for gravely ill children, and he had to watch his friends in the ward die, one after the other. During his stay<~~add comma he became continuously more and more mentally imbalanced<~~use "unbalanced" not "im-" and was denied release. Desperate to escape what he felt was a prison, Gackt started acting normally (like<~~use "as if" not "like" he was cured?) until he was released. This experience (incident, event?)<~~"experience" is fine; it's not an incident or event because there were many incidents and events over a period of time had a profound effect on him."

=)

"It was a hospital for gravely ill children, and he had to watch his friends in the ward die, one after the other. During his stay he became continuously more and more mentally imbalanced and was denied release. Desperate to escape what he felt was a prison, Gackt started acting normally (like he was cured?) until he was released. This experience (incident, event?) had a profound effect on him."

Can I say this and which words would be best to use?

Thank you very much! =D

You're very welcome.

=)

Yes, you can say it as:

"It was a hospital for gravely ill children, and he had to watch his friends in the ward die, one after the other. During his stay, he became continuously more and more mentally unbalanced and was denied release. Desperate to escape what he felt was a prison, Gackt started acting normally, as if he was cured, until he was released. This experience had a profound effect on him."

In this version, I have made the following changes:

1. Added a comma after "stay" to separate the clauses.
2. Replaced "imbalanced" with "unbalanced" as it is a more commonly used term.
3. Changed "like he was cured" to "as if he was cured" to make the phrasing more idiomatic.
4. Used the word "experience" instead of "incident" or "event" as it is a broader term that encompasses the series of events Gackt went through during his stay.

I hope this helps! Let me know if you have any further questions.