The leader is surprised. This isn't traditional, but it isn't unheard of either.
"Alright," she says with a nod. "Just wait until lights out."

Later, when the other girls are in bed, she turns out the light and motions you to come closer.
You decide that if this is what it takes to be accepted into the group, you'll do it.

She lays down on her bunk, and grabs your head suddenly.
You are pushed into her expanding vagina, the walls enveloping your head.

The combination of her pushing and the contractions of her muscles pull you inside her womb.
She gasps in pleasure, and her womb closes you in for the night. The constant sound of her beating heart lulls you to sleep.