Read Chapter 22. And if you don't want to, here's the summary:
They're manipulating the MC into having sex with Touko so that she's get pregnant and "give birth" to their dad. The MC is basically an unfortunate pawn for their plan. And later chapters revealed that other men of the same characteristics as MC have been scouted, though the MC is the only successful one so far.
That's... not what the chapter says. It's what a lot of people infer, but it could easily be a tradition for them to have dinner on a certain date for the fathers birthday,death etc and order his favorite desert.
She says just wait papa leading everyone to believe some weird reincarnation theory, but she could easily be referring to MC as papa this time and not dead papa, saying just wait and you'll get the child you want.
Or the scheme could be the OG Papa always wished to have a grandchild and their scheme is to grant his spirit that wish asap using MC and the daughter. The whole reincarnation thing seems like a pretty big leap the comments came up with.
Author keeps it very purposefully ambiguous.