na-adjective
Describes something related to the inner or psychological aspect of a person, as opposed to external appearance or circumstances.
彼は内面的な成長を遂げた。
He achieved inner growth.
外見よりも内
Inner beauty is more important than outward appearance.
外面的 means 'external' or 'outward', the direct antonym of 内面的, referring to surface appearances rather than inner qualities.
Derived from 内面 (ないめん, 'inner surface' or 'inner side') + the adjectival suffix 的 (てき, '-like' or '-al'). The combination creates a na-adjective meaning 'pertaining to the inner aspect'.