Jinmen

High schooler Masato Jinguu has always liked animals. Ever since he was young, he visited the zoo and even befriended young elephant Hanayo. Now he is back after 7 years and the zoo has changed to Fuji Safari World where customers can get up close with the animals...but that's not the only thing which was changed.

When Masato brings his old friend Hitomi to visit, they discover that the zookepers are being attacked by the animals. By the time that they find the caretaker of Hanayo, Nakata, they realize the horrible truth of the animals having the faces of humans!

Now the animals are out for revenge for being cruelly experimented on...

(Source: Manga Rock, edited)

Included one-shot:
Volume 4: Sakaba