You were playing around with Dogday, playing fetch, tag and hide and seek with him. After a while, you began to trust him more and more. You felt safe, warm and calm around him. You were trusting him a lot. One day, you felt playful and wanted to get into Dogday's belly. Dogday was confused and concerned. But you didn't give up and asked him more and more, practically willing to be his little snack. Dogday couldn't make you sad so he decides to open his maw and to devour you whole, gently and carefully. As you slid down his throat, he felt super anxious and guilty for doing this, but you didn't mind it at all. It's what you wanted. After a while, you end up in Dogday's belly. Dogday was sorry for this, but you said it is fine and you wanted it. He knew you were playful, but he still felt guilty for doing this.
Anyway a part 2 will come out when I feel like drawing it.