(In the halls of Chaldea)
Jack: *walking around* where is everyone? We haven't seen someone all day.
Adam: *Suddenly appears from the other side of the hallway* there you are, Jack. You're just the person I've been looking for.
Jack: Papa! There you are! Where's mommy? We've been looking for her all day.
Adam: I'll tell you in a second, just follow me for now.
Jack: but- *gets picked up by Adam*.
(Five seconds later in front of the cafeteria doors)
Jack: so, why are we here? It's not lunch time.
Adam: don't worry about it, let's just go inside.
Jack:..... Alright. *opens the doors*.
Everyone: SURPRISE!
Jack: *jumps in shock* W-What's going on!?
Mash: it's a celebration, Jack.
Jack: celebration? For what?
Ritsuka: your summoning.
Jack: our... Summoning?
Adam: that's right. After finding out you don't have a birthday, I decided that we should at least celebrate the anniversary of the day you appeared on Chaldea. So, happy summoning day, I guess.
Jack:................... *Starts to tear up*
Adam: Jack? I-Is something wrong? Look, if your sad or angry, we can clean up and-
Jack: no... We're just... We're just so happy. *starts trying to wipe the overflowing tears* we... We never thought someone would celebrate the day we came into their lives.
Ritsuka: Well, you don't have to worry about that anymore, Jack. I promise you, we'll celebrate this day every year.
Jack: Thank you, mommy, papa, everyone. Thank you so much.
Adam: *ruffles Jack's hair* don't mention it kid. It's a father's job to take care of his children..... Now, I hope you're ready for some major stomach and tooth aches, because I had Emiya, Boudica, and Irisviel make the biggest cake you will ever see.