 If you liked
Hatenkou Yuugi
|
 ...then you might like
Spiral: Suiri no Kizuna
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Well, both manga have warped logic and horrible mystery behind all events. In both of them there are an people toying with events and pulling the strings behind the scene of events. Some light-romance themes are well shown. And you will easily recognize some similarities beetwen main characters.
Also... Both are brutal, with quite a lot of blood and some characters dying.
There is also the cloning theme that appears in later chapters.