'I have decided... that I will dedicate my life and my body to you.'

The Arnauld Night Watch, an organisation of the King's direct guard, in the Kingdom of Arndt. Cecilia, second-in-command to Rudiger, the top-ranking Knight Commander, has feelings for Rudiger, who is always jokingly and sweetly toying with her. She has always been in love with her childhood friend, but now she is the deputy to the marshal. She is not allowed to bring her personal feelings into the relationship and keeps a lid on her feelings...? One day, Cecilia hears a strange rumour that 'women who meet Asmodeus become beautiful', and a series of unexplainable incidents occur. Cecilia sets out to investigate in order to protect the safety of the people, but ends up teaming up with an unexpected person who is also investigating the rumours...? The start of a mystery love fantasy in which Cecilia is overprotected by a superlative knight commander!