3 volumes and a few chapters of the 4th volume has so far come out. The last chapter on mangafox (ch.28, vol.4) has only gotten to the pool part with the girl who couldn't age as the attacker. I don't know if the manga in Japan actually has gotten further than that, but both the English and the Japanese wikipedia says that only 3 volumes has come out so far, which probably means that the 4th is still in progress and they haven't caught up to the anime yet. My guess is that the writer either told the anime makers what would happen, and that's how they could make the series, or that the anime makers got free hands to do whatever ending they liked which might differ from what the mangaka in the end will do.
