There's minor spoiler in my review.
Overall, it's Monster Musume mix with To Love-ru with High school dxd and Luminous Arc 2(game). The type of harem + fan service manga you see everyday, but this has stuffs that make the difference:

- It has a decent plot. It's not completely original but the manga is good at keeping me to keep reading for plot, and fan service.
- MC is not useless, he can fight, he improves himself. From someone who freaks out over a harmless youkai girl, later become someone who wants to protect innocent youkais and doesn't tolerate senseless killing. He can be a punching bag in many battles, he sometimes feels doubt and realizes his weakness, but he doesn't coward himself, and that is admirable. And he can either use his wood sword to fight or he can fuse with youkai girls to gain special abilities (or equipment). It's very similar to Engage system of Luminous Arc 2.
- This manga has fine art, and battle scenes look very well too.
- The characters may be somewhat like To Love-ru. Like some Yuki Rito accidents and the girls react like 75% of Yui. But each character has their own unique, so I highly enjoy reading the manga.
- Last but not least, don't be afraid when you know it has fan service, because the author doesn't overuse it and the service is not plain and surprisingly very well even for me who has grown hating ecchi scenes at some point.

I finish chapter 79 and write this review because I really encourage people to read this.