Cock Growth

Cock Growth is a magical skill learnable from Rinny; it costs 1 MP for each use.

Rinny would teach you that spell only after the Manor quest, and only if you ever witnessed her growing a cock before.

Note what this spell can't be used or learned if "Cock TF" shrine was disabled.

Primal use
When outside of combat, Lust Doll may use it to grow, shrink or modify their cock and/or balls without paying for the operation in Succubus Tower.

Additional uses
Additionally, this spell may be used in the following scenes, giving you additional scenes (assuming you have at least 1 mana to cast it):

Post-combat fun
Several enemies have post-combat scenes if you defeat them, which involve you forcing them to grow a dick. Currently, the following enemies have such scenes:
 * Bandit Girl
 * Succubus Teacher
 * Succubus Student

The pet
See also: Alissa

After completing Alissa's training, you may play with her at any time. Amongst other things, the option to grow her a dick would appear.

Spicing up things
See also: Second Marin's challenge

During the second Marin's challenge, after winning, you may insist on growing Marin a dick before forcing her to try her own medicine; she would reluctantly agree, but would insist on removing it afterwards, meaning it must be re-growth every time this scene is played.

Revenge
See also: Manor quest, Edith

After finishing the Manor quest, you can visit Edith in her cell. If doing so with Rinny by your side, the option to get revenge on her would appear. If you know the spell, the option to force her to grow a dick would appear.

Curing up complexes
One guy in the gym fears what his dick looks too small due to all his muscles. Using the cock-growing spell on him would help him dealing with this problem, but wouldn't provide any further scenes besides changing his responses if approached from now on; this scene exists purely as the small easter egg.

Dungeon
You may use this spell on Fawn in the dungeon after proving she can trust you as a dom when you successfully complete your first shibari outing with her tied up.