Reviewing this is kinda hard, I only finished the first volume by now but I really enjoyed it. The plot can be weird and perverted, and you can feel how it's inspired by other manga/anime, but somehow I find it really enjoyable to read.
The main character is a perv, but he starts liking this girl and wants to change. With the main character being a perv you can probably imagine its extremely ecchi. Also there is a lot of gore.
I personally love the art style, all the characters have nice designs and the Kaijins (the monsters they are fighting) are drawn with details which makes them creepier (in a good way).
The characters aren't written in a very original way, but honestly even tho I thought I'll hate the protagonist for being a perv, I actually found it funny how pathetic he can act at times, and seeing him wanting to change is also pretty nice. I can definitely see character development already.
It is enjoyable to read from my point of view. It has action, the main character can be funny, the main girl is definitely waifu, it has plenty of pretty girls, a lot of ecchi but even tho personally I'm not a fan of ecchi it was easy to just ignore.
There are definitely better things to read but I would recommend to give Kaijin Reijou a try!