Ai no Geboku -Hirusagari no Joou-sama-

Momoko is the royal princess of the kingdom from king's affair with the castle employee. Momoko attends a normal school till she is contacted by the kingdom secretary. It turns out that king has contracted some disease caused by the demon. Momoko is asked to lead the demon extermination party. Will she aim to fulfill her duty or seek for the common happiness?

[From vndbreview]