You didn't specify comedy, so I'm not sure how serious you want your series.
Hatsukoi Zombie Youkai Shoujo - Monsuga Yuragi-sou no Yuuna-san
All have some comedic elements, but Zombie is more shoujo/romantic, Monsuga has some battle elements, and Yuuna-san has occasional battle elements. Since you did say youkai/ayakashi, then I definitely think Monsuga is a good starting point.
Also Noragami, if you aren't reading that yet either since you also mention ayakashi.