It seems that he is suffering from chuunibyou.

He often behaves strangely because of his 'chuunibyou' (middle-school 2nd year syndrome).

He is showing behavior characterized by 'chuunibyou'.

I cannot forget that specific date.

His young and tender heart was very sensitive to new experiences.

His music conveys a sense of youth and tenderness, healing the heart.

Your actions are a clear case of copyright infringement.

Today is the death anniversary of my grandfather.

He made a deep apology.

I deeply apologized to him.