Obsessesion and infatuation, though similar Tezuka, are not quite the same in this instance.

It is very much possible to become infatuated with someone at first glance. Be it by a phrase or inflection in someone's voice that may strike a chord in your heart. Maybe you'll be warmed by a gaze or an intriguing remark goes straight to your soul.

It can also be as simple as physical attraction.