That first passionate kiss causes dopamine to spike in the brain. Its a give-me-more insatiable hormone all about pleasure; when we first fall in love and have those over-the-moon thoughts, thats dopamine. Incidentally, it affects the same part of the brain as cocaine, making us crave for more.

Does a first kiss really matter?

It really does not matter who you share your first kiss with. The likelihood of you ending up with the very same individual you share this magic moment with is highly unlikely.