From Sweet Indulgent:

Salamander is a demon with a mission. The Dark Lord is amassing his own harem using his powerful charm magic, leaving practically no woman untouched. The council can't stand such a man-filled world and order Salamander to hinder the Dark Lord's plans. However, the only one who can defeat him is the hero that is marked with a star-shaped holy symbol. Salamander is commanded to locate and protect that person.

Salamander soon finds (and is subsequently knocked out by) the hero, who is a bright, independent, and strong high school girl named Aoki Tsubasa. After learning that the hero is a girl, the council members get excited and announce a change of plans. Since Salamander is good-looking and the hero is a woman, the obvious path is that she must fall in love with him! And he can't return until she does. Thus Salamander is reluctantly caught up in the Big Lovey Dovey Plan!