Since this is the first review on this manga, I thought I'd introduce you, the potential reader, to its theme, tone and mood rather than focusing on specific areas and critiquing them.
The manga begins in a modern day setting where a group of college students are led by their classmate to the island she comes from. Now of course, this island is not what it looks like, with the sidelong glances of the hosts and the simmering mood that is present. This mood culminates in a hunt for "intruderss" (the college students) who are not allowed to witness the "ceremony" of the island. I'll leave the rest for you to find out but it's fair to say that the story goes down a dark path and over the duration of the manga (so far) it continues to decline into even darker themes.
Finally, to wrap up this review, I'd like to focus on Tarou, the protagonist of the story, who is delightfully explored over the duration of the manga so far. His descent towards madness is delightfully entertaining and it's interesting to see what lengths he'll go to in order to achieve his goals, something which many mangas fail to encapture.
Overall, this manga is not a masterpiece and neither is it spectacular. It is a good read with a plot that twists and turns, making the manga as a whole, very entertaining. A solid 7/10 from me.