What is the first moment of amor relationship Nagisa-Tomoya?

You know that a major amor story in this animê is around Nagisa and Tomoya relationship. You also obviously know that in Chapter 22 Tomoya finally confess his amor directly to Nagisa and they start become lovers.

But I believe that there are some moments before it that shows Nagisa and Tomoya feel in amor each other.

So, I want to hear your opinion about the first moment seen in this animê that show Nagisa and Tomoya feel in amor each other. You can mention the chapter which shows that moment and the reason you choose it as the first moment.

I amor the romantic plot shown is this anime, so I believe get some interesting moments in it with all of your opinion in this question.

Thank you for your answers. :)