Alternatively, you can setup different difficulty levels, where the grind itself can be eased.
I can't remember how much corruption you'd gain from the "tease them" option or working.
But for example: The player on Normal difficulty, the mc will spread corruption by one, for the cost of consume time. If the player decide to take on a "Story mode" type, this action would still consume the time, however it would give five to ten corruption.
Same fix can be used on money as well!
What would this solution do? Nothing but reduce repeating one action over and over again, to actually reduce the grind, within a reasonable, and non-exploiting way. And since you wouldn't grind one action over and over alone, the said sequence would be still required, but it will be available much faster, also making the player playing the game.
This solution is walkable, for various reasons:
1. Removing an exploit gate
2. People whom want to focus on certain character(s) only, can enjoy the benefit of the natural corruption progress.
3. Reach the reach either the highest corruption level and/or become a millionare only because we can shower would generally ruin the experience.
4. Potentially more ways to interact with the NPC's outside of story to gain corruption, money, something else.