Every collection has a start (Des)

Achievement unlocked: every collection has a start.

You enslaved your first monster girl, how many can you get into your little harem?

+5 endurance (you'll need it)

Training crop (you can use your own carrot, but here's a stick.)

150xp

500$ (treat your girl to a nice gift, bitches ain't cheap)

Reference
Unlocked in Chapter 77 "Daugher Of The Glade? Who's Your Daddy Now?"