、。
He fell in love with Akiko the moment he met her.
Literal
Akiko [dative-に] met that moment [from-から], he [topic-は] Akiko [subject-が] become-liked.
A good example of how 好きになる ('become liked') works: 明子が好きになる = '[something] becomes the state where Akiko is liked.' The が marks what's liked, not what does the liking — a Japanese-specific construction where adjective-like predicates take が for their internal argument. 会った is the past of 会う, with に for the person met. The その瞬間 ('that moment') + から ('from') combines to emphasize a sharp turning point.