The reason why Prince Cecil need to have a lover is that
if he doesn't, he would get bored and eventually brought ruin to his country. One of them was he will became war fanatic and brought ruin to not just his country but others as well.
I didnt mean to sound rude but i think the translator made mistake on Bertia wanna be a nun, its supposed to be Bertia wanna be a monk. I know since i had read the novel, but if the manga raw really did said nun then ok.
@Opelia
Definitely a tranlsation error. She even says in the chapter that she'll dedicate her life to buddah and I don't know of nuns who shave their heads, but monks definitely do.
I'd thought that the annulment is the end of the game. The fact that it's a midway point is very interesting for me. This'll be new territory (though, mostly because I haven't seen much material that starts from before and has reached the annulment event).
Doubt that Turkey light spirit is really dead as no one rammed it through with a speciality blade or it was killed by another spirit. That little brat simply drained its battery and had to disperse. Give it a few year/decades and it probably be able to pull itself back together.