Not bad but a bit confusing. Thought the character actually had a sister but it was just a girl who he met.. and no matter what happened in the end she killed over 100 other kids didn't she? pretty fucked up.
Some parts of the translation are pretty bad, especially in the last volume. You can tell it got cancelled before the mangaka could fully express the story he had in his head, but on the whole I suppose it was a fine series.